Wednesday, January 14, 2015

A Probability for Dog Doodoo

A pet peeve of many statisticians is the transposition fallacy—misconstruing the probability of the data given the hypothesis as the probability of the hypothesis given the data. In general,

P(data | hyp) ≠ P(hyp | data).

The term “pet” is particularly apt in the case of yesterday’s PBS “Here and Now” interview on animal DNA analysis in forensic science. The program’s host interviewed WBUR’s Vicki Croke, who has written an engaging and informative account of “Pet CSI: How Dog and Cat DNA Nabs Bad Guys.” She begins with the following case:
On Sept. 14, 2000, Wayne Shumaker, 58, Corby Myer, 30, and Lynn Ganger, 54—three carpenters building a barn loft at an upscale property near Lakeville, Indiana—were bound and shot execution style during an armed robbery. Less than two years later, the triggerman in the case, Phillip Stroud, was found guilty on all three counts of murder and sentenced to life in prison. The criminal was done in—at least in part—by the dog droppings he had stepped in during the commission of the crime. It turns out that dog feces not only messed up his sneakers, but his defense too. It was a simple mistake that was exploited by the prosecution using some new and very sophisticated science. Samples from Stroud’s sneakers were compared to dog feces at the barn. Through DNA analysis (as they exit, feces snag DNA-carrying epithelial cells from the colon), the specimens turned out to be a perfect match—proof positive that the defendant had been present at the scene of the crime.
In the interview, Ms. Croke elaborated on "proof positive" as follows:
[T]he lab needs to calculate probabilities. How common is this particular pattern of DNA in the wider population? In other words, how likely is it that this hair could have come from any other dog or cat than the one linking the criminal to the crime? In the triple murder case we were talking about, the probability that the feces on the suspect’s sneaker came from any other dog than the one at the scene of the crime was one in ten billion!
Here and Now's webpage thus refers to "a probability test to determine how likely it is that the DNA comes from any other animal in the area."

These characterizations are fairly typical examples of transposition. The data in the triple-murder case are the pair of DNA profiles that are said to match. The hypothesis is that the source of the sneaker DNA is a different dog. We’ll call this the defense hypothesis, def-hyp. Assuming no laboratory error in profiling ever occurs, the probability of the data—the matching profiles—given that they came from different (and unrelated) dogs is the frequency of the profile in the “wider population.” Let’s assume that one in ten billion is a good estimate of that probability. That is,

P(data | def-hyp) = 1/10,000,000,000.

Is “the probability that the [DNA] came from any of other dog” also 1/10,000,000,000? Not exactly. This probability is P(def-hyp | data). According to Bayes' rule, it depends not only on P(data | def-hyp), but also on two additional probabilities. For one thing, we need to know the probability of the data given the prosecution’s hypothesis, P(data | pros-hyp). This probability is 1 (if the lab is certain to declare a match when the two samples really contain the same dog's DNA).

Another factor to consider is the prior probability of the defense hypothesis, P(def-hyp). How many alternative dogs could have been crossing defendant’s paths in the weeks before the murder? One thousand seems like a lot. If we take the prior odds for the defense hypothesis to be 1,000:1, then the match to the dog doodoo in the barn reduces these odds to 1,000:10,000,000,000 = 1:10,000,000.

What the moral? Transposition is wrong, but almost everybody, from journalists to jurors, does it. A DNA match to a random, unrelated dog may be a one in ten-billion event, but it does not follow that the probability that defendant stepped on stuff from an unrelated dog is one is ten billion. That said, if the random-match probability is as infinitesimal as one in ten billion, the probability of the defense hypothesis (about an unrelated dog being the source of a true match) is still doggone small. Transposition should be avoided, but it is not always the most grievous of errors.

Sunday, January 4, 2015

Buza Reloaded: California Balancing

This is the fourth installment on Buza II, the opinion of the California court of appeal that invalidates the state's DNA-on-arrest law. It discusses the part of the opinion that argues that the balance the U.S. Supreme Court struck in Maryland v. King is either flatly wrong or wrong for California. In giving substantial weight to concerns over "familial searching" and the information content of DNA samples, the opinion assumes that it is appropriate to strike down a law that is constitutionally reasonable as currently implemented because future developments might make it unreasonable as then implemented. This premise is highly contestable.

Formally, the conclusion that California's DNA-BC (Before Conviction) law is unreasonable under the Fourth Amendment as it appears in the California Constitution does not imply that it is unreasonable under the Fourth Amendment as it exists in the U.S. Constitution. California is a sovereign state of the Union, and its courts can read different meanings into the words of its constitution. But many of the reasons the Buza II opinion gives for its conclusion—if correct—also apply to nearly all of the 25 or so DNA-BC laws on the books, and the opinion itself indicates that, in large part, the divergence between Buza II and King emanates from the California judges’ outright disagreement with the Supreme Court's balancing in King.

To begin with, the California judges complain that King “unjustifiably dismissed concerns about the extent of the personal information contained in DNA samples by limiting ... attention to the profile used in DNA databanks, as currently restricted by statutes and scientific capability.” One might expect that this observation immediately would be followed by the undeniable fact that the entirety of a person’s genome contains some medically significant information that would not otherwise be known, such as predispositions to certain diseases. Testing for these alleles (or for markers for them) would pose significant privacy issues (which is why such testing generally is prohibited without the individual’s consent).
But the opinion veers off into a superficial discussion about the CODIS profile itself. The problem, according to Buza II, is that the profile can be used not merely to identify an individual whose DNA is taken when he is arrested, but also sometimes can be used to identify a first-degree relative as a likely source (when the arrestee’s DNA is a close mismatch to the crime-scene sample). This “familial searching,” as the court calls it, is a “factor not relevant to identity,” and therefore “present[s] additional privacy concerns.”

The second part of this statement is true enough. Like a perfect match, a close mismatch is relevant to the identity of the DNA source, but it also reveals that the arrestee could be genetically related to the source of the crime-scene DNA. 1/ Consider the “Grim Sleeper” case of serial rapes and murders in the Los Angeles area, with years of apparent inactivity between some of the attacks. Trawls of the database proved fruitless—until Christopher Franklin was convicted of a felony. His DNA profile did not match the Grim Sleeper’s, but it lined up with it in a manner that would be expected if the two were father and son. This led investigators to Christopher’s father, Lonnie Franklin, Jr. In this way, Lonnie emerged as a suspect only because of his son’s conviction. (His DNA profile was not in the database because his arrests had occurred before California had a database.) Now he stands accused of ten murders.

People v. Franklin reveals an important fact about kinship trawling. In Franklin, it is difficult to discern the slightest “additional privacy concerns.” That Lonnie was Christopher’s father was a publicly known fact, not a private secret. Furthermore, Lonnie can hardly claim to have a legitimate Fourth Amendment interest in keeping secret the fact that it was his DNA that was found on or around murdered women. 

Of course, there could be other cases in which the familial relationship between the database inhabitant and the culprit was not known to one or both of the genetically related individuals. In such situations, the claim to a right to keep the genetic relationship secret is more plausible. But the existence of possible cases of this kind does not demonstrate that the occasional legitimate privacy interests that might be affected by the rare, "other-directed" trawls (that look for people outside of the database) outweigh those of the government.

In particular, for Mark Buza and his relatives to have an additional privacy interest compromised by the arresteee database, at least two conditions would have to be fulfilled. First, California would have to initiate other-directed trawls of its arrestee database. It has never done so, and it cannot do so under the policy its Department of Justice has adopted for such database trawling. This policy confines the other-directed trawling to convicted-offender databases. Second, Mark Buza would have to have publicly unknown first-degree relatives whose DNA profile would be close enough to Mark’s to implicate them in other crimes via a kinship match to Mark’s profile.

On its face, the first condition suggests that the parts of the opinion discussing “familial searching” are inapposite. Why strike down a law because of what could be but is not? Nonetheless, the Buza court’s sensitivity to the possibility of a change in the state’s DNA-BC practice might be seen as prescient rather than premature. From the outset, an argument against DNA databases has been mission creep. Once the database is established, the state will be tempted to use it for additional and more insidious purposes. To guard against this outcome, the argument goes, society should bind itself to the mast in anticipation of an irresistible siren song.

There are situations in which this self-disabling strategy is advisable. Indeed, much of the Bill of Rights constrains the majority from doing what seems expedient or appealing in the heat of the political moment. But it is not so clear that a handful of judges should block the democratic decision to allow DNA-BC to be used in acceptable ways that advance law enforcement on the ground that the system might be administered in unacceptable ways at some future time. If and when a jurisdiction combines other-directed trawling and DNA-BC, courts can consider whether that type of trawling is so serious an invasion of privacy as to render it unconstitutional. Using the mere possibility of a correctable change in the allowed uses of the DNA data to strike down the collection and otherwise acceptable uses of the data seems Draconian.

Moreover, it is inconsistent with Buza II’s effort to distinguish the Maryland practice. Presiding Justice Kline emphasized the existence of a Maryland statute banning familial searching. But as Chief Judge Alex Kozinski of the U.S. Court of Appeals for the Ninth Judicial Circuit tartly observed in oral argument in Haskell v. Harris (a separate case challenging California DNA-BC law), statutes can be changed too. The logic of Buza II—that databases that are constitutionally reasonable (as currently implemented) but might become unreasonable (as implemented in the future) are constitutionally unreasonable ab initio—would render the Maryland law on DNA-BC unconstitutional.

Despite these problems, Buza II applies the nip-it-in-the-bud reasoning not only to DNA profiles but also to samples. Displaying little knowledge of behavioral genetics, the court invokes “the pedophile gene” and “the violence gene” that, it imagines, might well be discovered some day. It predicts that “surely law enforcement will seek to mine genetic information for that ‘identification purpose.’” 
But there is no good reason to believe that the word “identification” as used in DNA-BC laws would permit predictive genetic testing for these behaviors, and the court makes no attempt to explain why such testing could not be condemned as constitutionally unreasonable if and when the time arises.

My criticism of the court of appeal's reliance on dystopic visions of the future is not based on naive faith in the goodness of police and law enforcement laboratories. Courts need not—and should not—trust law enforcement to exercise perfect self-restraint in investigative methods that easily can be abused. Before approving a DNA database system, they should satisfy themselves that sufficient safeguards against predictable abuses are in place. But if such protections are present, courts should not invalidate a system because the safeguards might be removed or might cease to be effective in the future. In this case, might does not make the decision right.

Note
  1. Confusingly, the court presents this fact as if it "disproves the King majority’s assumption that 'the CODIS loci come from noncoding parts of the DNA that do not reveal the genetic traits of the arrestee.'" Some noncoding DNA does affect visible traits of an arrestee, but the CODIS loci, as far as current science can tell, do not reveal much about any phenotypes. Because all DNA sequences are inherited, however, including those that King (also confusingly) calls "junk," the ones that vary across individuals, can be used in kinship analysis. In fact, the sequences that do give rise to individual traits often are the best for this purpose because they tend to be extremely variable within populations.
References
Closely related postings

Thursday, January 1, 2015

Buza Reloaded: Fourth Amendment Balancing


This is the third installment on Buza II, the opinion of the California court of appeal that invalidates the state's DNA-on-arrest law. It comments on the court of appeal's treatment of the definition of a "search" and the court's claim that the reasons the Supreme Court gave in Maryland v. King for upholding post-arraignment DNA collection from Alonzo King are "completely inapplicable" to taking DNA from Mark Buza during booking.

Having described the scope of totality-of-the-circumstances balancing in exceedingly generous terms, Presiding Justice Kline turns to a logically prior Fourth Amendment question—should the DNA collection from Buza be considered a search under the Fourth Amendment? This definitional issue is a condition precedent to reasonableness balancing in that the state has no burden of showing reasonableness if it does not conduct a “search or seizure” within the meaning of the amendment.

Again, the court reaches the correct conclusion—of course there was a search—but the exposition raises some questions. Presiding Justice Kline wrote that
Nonconsensual extractions of substances that may be used for DNA profiling are “searches” entitled to the protection of the Fourth Amendment. (King, supra, 133 S.Ct. at p. 1969 [buccal swab]; Schmerber v. California (1966) 384 U.S. 757, 767-771 (Schmerber) [blood]; People v. Robinson, supra, 47 Cal.4th at p. 1119 [blood]; Skinner v. Railway Labor Executives’ Assn. (1989) 489 U.S. 602, 616-617 [breathalyzer and urine sample]; Cupp v. Murphy (1973) 412 U.S. 291, 295 [finger nail scrapings].) The physical intrusion involved in the buccal swab procedure used in the present case has been viewed as minimal. (King, at p. 1969.) The collection of the DNA sample, however, is only the first part of the search authorized by the DNA Act; the second occurs when the DNA sample is analyzed and a profile created for use in state and federal DNA databases. The latter search is the true focus of our analysis. (Brackets in original).
Most of this paragraph is gratuitous. Why not stop with the irrefragable proposition that King held that buccal swabbing is a search? Every Justice of the U.S. Supreme Court accepted this premise, and not one maintained that there was one search followed by another search. According to the King majority, "using a buccal swab on the inner tissues of a person's cheek in order to obtain DNA samples is a search" simply because "[v]irtually any intrusion into the human body will work an invasion of cherished personal security that is subject to constitutional scrutiny.” 133 S.Ct. at 1969 (internal quotations, citations, and alteration omitted).  “The ... intrusion [although] negligible ... is still a search as the law defines that term.” Id.

In contrast, whether trawling a database for a DNA match to the DNA profile derived from the sample acquired by the physical intrusion is a “latter search” is an open question. Federal appellate courts have reached different conclusions about it, and the King Court did not discuss it (despite the insistence of King’s counsel at oral argument that DNA analysis and trawling is a search in itself). To be sure, the nature of DNA profiling and trawling is “of central relevance,” King, 133 S.Ct. at 1969—but only on the distinct question of whether the search is reasonable. Id.

Before turning to that question, the Buza II court expressed some sympathy for Justice Scalia’s “piercing” dissent. This position is at odds with Presiding Justice Kline’s description of the Fourth Amendment as always accommodating balancing, since the entire theory of Justice Scalia’s dissent was that the reasonableness of DNA sampling on arrest is not to be determined by weighing individual and state interests, but by a putative categorical rule against certain suspicionless searches

Be that as it may, the Buza II court maintained that King’s “reasons for upholding the Maryland law [are] completely inapplicable to California’s.” That conclusion seems precipitous. There is ample room to debate the value of arrestee sampling and the significance of the differences of the Maryland and California statutes. Indeed, I have written that Justice Kennedy’s reasoning in King is “contrived,” but only because a candid approach to totality balancing (or, preferably in my view, toward creating a new categorical “biometric exception” to the general rule against warrantless searches) has to incorporate the power of DNA to solve cases and deter crimes sooner rather than later (or not at all). 1/

But surely King’s detention-related reasons for DNA testing cannot be dismissed as “completely inapplicable.” For example, Buza II cited the fact that whereas the California law covers all felony arrests, the Maryland law encompasses only arrests for “murder, rape, first-degree assault, kidnaping, arson, sexual assault, and a variety of other serious crimes.” King, 133 S.Ct. at 1967. The supposition that DNA from individuals arrested for nonviolent felonies is less likely to provide a link to an unsolved crime hardly means that the DNA is devoid of investigative value. Car theft is not a violent crime or a burglary, but at least some car thieves leave behind traces of DNA while committing more serious crimes

Furthermore, even the more sensible reasoning that arrestee DNA is, on average, less valuable to the state for some felonies than for others does not distinguish the demands the states made on the defendants in King and Buza. Mark Buza, after all, was caught committing arson—surely a serious crime. Why is the Buza court addressing the law as applied to a hypothetical person at another time? Under established Fourth Amendment doctrine, Buza was justifiably arrested for arson. As such, he lacks standing to assert the rights of individuals arrested for much less serious offenses. If it was constitutional to have compelled King to give a DNA sample—which is what the Supreme Court held—why is not equally constitutional to have ordered Buza to give a DNA sample? The answer cannot be that the Supreme Court in King was confronted a serious felony arrest. The court of appeal in Buza likewise was confronted with a serious felony arrest.

Indeed, the Buza opinion itself backs away from the extreme position that King’s reasoning is “completely inapplicable.” The court announces that it is not actually deciding the fundamental question of “whether these differences require a different resolution of the issue from that of the King majority.” It ends its Fourth Amendment analysis with more of a whimper than a bang, dismissing the entire issue: “Our conclusion that the DNA Act is invalid under article I, section 13, of the California Constitution renders it academic whether the Act is also invalid under the Fourth Amendment.” The court is convinced that the differences “significantly alter the weight of the governmental interests and privacy considerations to be balanced in determining constitutionality under the Fourth Amendment,” but it seems less certain that this alteration truly produces a different result.

To reach a different result, the Buza II court performs its own balancing under an unusually demanding balancing test. The next installment comments on this California balancing.

Note
  1. David H. Kaye, Why So Contrived? DNA Databases After Maryland v. King, Journal of Criminal Law & Criminology, Vol. 104, No. 3, pp. 535-596, May 2014, available at http://ssrn.com/abstract=2376467
Closely related postings

Monday, December 22, 2014

Buza Reloaded: The Fourth Amendment Framework

This is the second installment of remarks on Buza II, the opinion of the California court of appeal that invalidates the state's DNA-on-arrest law. It questions the opinion's expansive view of when "totality of the circumstances" balancing is appropriate under the Fourth Amendment

The Buza II court begins its legal analysis with the reasonableness clause of the Fourth Amendment. Omitting the clause that refers specifically to judicial warrants, the opinion tells us that "[t]he Fourth Amendment protects '[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures' . . . ." However, the court adds that "[s]ubject only to a few specifically established and well-delineated exceptions not applicable here, warrantless searches are per se unreasonable under the Fourth Amendment." Of course, if this were literally true, the case would be over, since California had no judicial warrant to compel Buza to submit to DNA extraction, and there was no "applicable exception." (The search-incident-arrest exception only permits warrantless searches for weapons or evidence that the arrestee might reach.)

The court of appeal apparently does not believe that there is a true per-se-unreasonable-with-exceptions (PSUWE) rule. Instead, it presents the absence of a warrant as a mere burden-shifting device.The state, it says, "thus bears the burden of showing that the search at issue is reasonable and therefore constitutional. (People v. Williams (1999) 20 Cal.4th 119,127.)" This interpretation cuts the heart out of the PSUWE rule and does not flow from People v. Williams. In Williams, the California Supreme Court wrote that when moving to suppress evidence, "defendants have the burden of (1) asserting the search or seizure was without a warrant, and (2) explaining why it was unreasonable under the circumstances." 83 Cal.Rptr.2d 275, 282 (Cal. 1999) (emphasis added). It seems odd to cite the case for the opposite proposition--that the burden is on the state.

But this questionable use of precedent is a minor sin. The more disturbing aspect of Buza II's exposition of the Fourth Amendment lurks in its view that a court always can find reasonableness "by examining the totality of the circumstances," which is to say, "by balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of legitimate governmental interests." The U.S. Supreme Court cases cited for this open-ended approach to reasonableness do not dilute the PSUWE rule to this degree.1/

In fact, if the Buza II court's claim that every warrantless search can be saved by a finding of reasonableness under the circumstances were correct, the Supreme Court would not have had such a difficult time explaining in Maryland v. King why Maryland's pre-conviction DNA law was subject to a balancing test. Rather than announce that "we always balance," Justice Kennedy, writing for the majority, tried to weave together specific features of other cases departing from the PSUWE framework in favor of a direct balancing test. Whether the resulting tapestry is so poorly woven that it is about to unravel has been debated, 2/ and Buza II misapprehends the but the Court itself has not officially abandoned the PSUWE framework. Indeed, soon after King, in holding that a warrantless search of a cellphone during an arrest was impermissible, the Court reiterated that "[i]n the absence of a warrant, a search is reasonable only if it falls within a specific exception to the warrant requirement," Riley v. California, 134 S.Ct. 2473, 2482 (2014), and demanded that "even when a cell phone is seized incident to arrest," id. at 2494, the police had better "get a warrant." Id. at 2495.

Although the Buza court is thus mistaken in its treatment of the threshold question of when direct, totality balancing is permissible, King does hold that a form of balancing is required for warrantless DNA swabbing. In the next installment, I will consider the court of appeal's effort to dismiss this balancing, as performed by the Supreme Court, as "completely inapplicable."

[Next installment]

Notes
  1. See David H. Kaye, On the “Considered Analysis” of DNA Collection Before Conviction, 60 UCLA L. Rev. Disc. 104 (2013); David H. Kaye, Why So Contrived? DNA Databases After Maryland v. King, 104 J. Crim. L. & Criminology 535 (2014).
  2. Compare Erin Murphy, License, Registration, Cheek Swab: DNA Testing and the Divided Court, 127 Harv. L. Rev. 161 (2013), with David H. Kaye, Maryland v. King: Per Se Unreasonableness, the Golden Rule, and the Future of DNA Databases, 127 Harv. L. Rev. Forum 39 (2013).
Closely related postings

Sunday, December 7, 2014

Buza Reloaded: Court Shifts Ground But Again Invalidates California’s DNA-on-arrest Law

Buza I
For the reasons we have set forth, we conclude that the DNA Act ... unreasonably intrudes on such arrestees' expectation of privacy and is invalid under the Fourth Amendment of the United States Constitution.
Buza II
For the reasons we have set forth, we conclude that the DNA Act ... unreasonably intrudes on such arrestees’ expectation of privacy and is invalid under article I, section 13, of the [California] Constitution.

Nearly seven years ago, Mark Buza set a San Francisco police car on fire to protest what he said was a corrupt government. Spotted running from the burning car, he was promptly arrested and brought to the county jail. There, he engaged in a second act of defiance, refusing to allow police to swab the inside of his cheeks to acquire a DNA sample. (He did, however, acquiesce in fingerprinting and writing a signature.) After his conviction for arson-related crimes as well as the separate offense of refusing to submit to DNA sampling, a court ordered him to give a sample before sentencing. In a third act of resistance, he refused, but when the court issued a further order allowing police to use force, he finally submitted to the swabbing. His DNA profile entered the California database, apparently without incriminating him in any other crimes.

The California Court of Appeal reversed the conviction for resisting “the seizure of his DNA at a time when he was entitled to the presumption of innocence, and [when] there had been no judicial determination of probable cause to believe he committed the offense for which he was arrested ... .” California's DNA-collection law, the court reasoned, “violated his Fourth Amendment right to be free from unreasonable searches and seizures.” The court expressly declined to consider whether compelling DNA collection before a judicial finding of probable cause violated Buza’s “right to privacy under article I, section 1, of the California Constitution.”

The California Supreme Court granted review, vacated the appellate court’s judgment, and ordered that court to reconsider its reversal of the DNA-refusal conviction in light of the United States Supreme Court’s decision in Maryland v. King, 133 S.Ct. 1958 (2013).

In a lengthy opinion issued four days ago, the Court of Appeal, like Buza himself, stuck to its guns. For a second time, it held that the California initiative that mandates DNA sampling on arrest (and that has been upheld by several other courts) is unconstitutional. However, the court shifted ground. Now Presiding Justice Anthony Kline wrote: “we question whether King establishes the validity of the California Act’s application to arrestees under the Fourth Amendment. We base our decision, however, solely upon article I, section 13, of the California Constitution, which in our view undoubtedly prohibits the search and seizure at issue.” (Emphasis added.)

I’ll leave it to California’s bar, bench, and scholars to debate how and why the Court of Appeal can be so certain that California’s constitution, which essentially reproduces the words of the Fourth Amendment, compels a different result than King might warrant. Here, I want to consider the Court of Appeal's analysis of the outcome that should follow under the U.S. Constitution as construed in King.

[Next installment]

Closely related postings
References

Thursday, October 30, 2014

Another Disgusting DNA Case: Please Flush!

A quick update to the disgusting DNA report of last March (The Whooper Stopper). Following up on a report from KOAT-TV in Albuquerque, the Associated Press reported that a man helped himself to $250,000 worth of jewelry from a home while the owners were on vacation and neglected to flush whatever he left behind in the toilet. Is there is a lesson to criminalists here: swab toilet seats and handles to catch more considerate burglars as well? Probably not. Cf. Peter Gill, Misleading DNA Evidence: Reasons for Miscarriages of Justice (2014) (discussing the interpretation of touch DNA).

Far more offensive is a case reported by the same TV station in 2011. It seems that a 31-year-old Sunflower Market employee offered a woman what he said was a free yogurt sample. Incredibly, it was his semen. After pleading guilty, he was sentenced to a two-year prison term.

Tuesday, October 7, 2014

The Supreme Sound of Silence: Same-Sex Marriage and DNA Databases

The big news among Supreme Court watchers is the big dog that did not bark in the night — the Court’s denial of petitions for certiorari in seven cases striking down bans on same-sex marriage in Indiana, Wisconsin, Utah, Oklahoma, and Virginia. [1] A denial of a cert petition has no precedential value. It does not mean that the Court approves of the decision below—or that it disapproves of it. It means that, for unstated and often banal reasons (the Court receives some 10,000 petitions a year [4]), no more than three Justices voted in favor of review the decision below. (By convention, it takes four votes to grant the writ that triggers the Court’s review of the case on the merits.)

The Court watchers are treating the rejection of the writs here as a “tacit win to gay marriage” on the theory that it means that if and when the Court chooses to confront the issue, a majority of states will have sanctioned same-sex marriage, making it more likely that the Court will accept the argument that the Constitution forbids limiting the institution of marriage to couples of the opposite sex. [3]

This predicted dynamic was evident in the Court’s handling of laws requiring routine DNA collection for law enforcement databases. No appellate court ever struck down a law requiring convicted offenders to provide samples, and for some thirty years, the Court invariably denied petitions for review in those cases. Only after Maryland’s highest court essentially invalidated that state’s law providing for DNA collection on arrest did the Supreme Court step in. By that time, every state had a DNA database for convicted offenders, and a majority had extended them to require pre-conviction DNA sampling. Every state signed an amicus brief urging the Court to uphold the practice. The Court split 5–4 on the constitutionality of pre-conviction DNA testing. Had the states and the federal executive branch not presented so unified a front in favor of expansive DNA collection, the outcome could have been different. [2]

References
  1. Amy Howe, Today’s Orders: Same-sex Marriage Petitions Denied, SCOTUSblog, Oct. 6, 2014, 10:41 AM, http://www.scotusblog.com/2014/10/todays-orders-same-sex-marriage-petitins-denied/
  2. David H. Kaye, Why So Contrived? DNA Databases After Maryland v. King, 104 J. Crim. L. & Criminology 535 (2014), available at http://ssrn.com/abstract=2376467
  3. Adam Liptak, Supreme Court Delivers Tacit Win to Gay Marriage, N.Y. Times, Oct. 7, 2014, at A1, http://www.nytimes.com/2014/10/07/us/denying-review-justices-clear-way-for-gay-marriage-in-5-states.html
  4. Robert M. Yablon, Justice Sotomayor and the Supreme Court’s Certiorari Process, 123 Yale L.J. F. 551 (2014), http://yalelawjournal.org /forum/justice-sotomayor-and-the-supreme-courts-certiorari-process.html