The Rap Sheet

Bitemark evidence is a tool that prosecutors sometimes use to connect defendants to crimes. The testimony of a bitemark expert (who carries the fancy, jury-impressing title of "forensic odontologist") usually goes something like this: "I compared the teethmarks found on the victim's right arm with the defendant's dental prints.  In my opinion, a match exists; the defendant was responsible for the teethmarks." 

Though judges routinely admit bitemark testimony, recent studies have undermined its reliability.  Unlike the generally-accepted principle that fingerprints are unique, the uniqueness of dental patterns has never been established. Moreover, bitemark experts usually have to base their conclusions on fragmentary patterns -- say, the marks left by a few teeth. Finally, the proficiency of bitemark experts is uncertain because they have never been scientifically studied.  Thus, it's no surprise that a number of defendants who have been cleared by DNA analysis after they have begun serving their sentences were convicted partly on the basis of mistaken bitemark evidence.

In the future, criminal defense attorneys will no doubt more aggressively challenge the admissibility of bitemark evidence. As "gatekeepers," judges have to remember that prosecutors who want to rely on bitemark evidence have the burden of establishing the reliability of its underlying principles.  If they cannot do so, judges should disregard the fancy trappings of forensic odontologists (advanced degrees, publications, professional associations, good molars) and tell them to bite the dust.

In the 2004 "Crawford case", the U.S. Supreme Court interpreted the Sixth Amendment's Confrontation Clause to require prosecutors to present live witnesses rather than hearsay whenever the hearsay was "testimonial." The decision has given rise to lots of commentary and court opinions (many of them conflicting) about whether particular types of hearsay are testimonial.  For example, if a domestic violence victim makes an emergency call to a 911 operator, the victim's statements are likely not to be testimonial, meaning that prosecutors can, if necessary, offer a transcript of the call into evidence if the victim refuses to come to court and testify.  On the other hand, if the domestic violence victim talks to a police officer once the emergency is over, the victim's statements are testimonial. If the victim refuses to testify, the prosecutor cannot call the police officer as a witness to testify to what the victim said.

One of the elephants in the Confrontation Clause room is whether lab reports are testimonial.  Every day, hundreds of doctors and other technicians conduct autopsies, test substances to determine whether they are illegal drugs, determine the alcohol context of blood or urine, etc.  They prepare reports of their findings and before Crawford most courts routinely admitted these reports into evidence at trial under long-established hearsay exceptions for business or official records. But if these reports are testimonial, defendants would have the right to insist that the report preparers testify in person.  The ramifications of such a result are potentially huge. If forensic experts have to testify, at the very least trials become longer and lab backlogs will continue to grow because experts who are testifying (or, more likely, waiting to testify) are not conducting tests.

Sometime in early 2009, the U.S. Supreme Court will likely issue an opinion addressing these issues.  The case is Melendez-Diaz v. Massachusetts, and the Court heard arguments in the case in November 2008.  Forensic lab reports certainly look testimonial in that they are prepared by government officials who usually are aware that they may be offered into evidence at trial.  Prosecutors counter that lab reports are not testimonial because they are objective, especially since many of them are simply machine-generated.  Prosecutors also argue that if defendants really want report preparers to testify, the defendants can call them as their own witnesses.

The outcome of Melendez-Diaz is likely to have a huge impact on the day-to-day functioning of the criminal courts.  My prediction: Since the Supremes have been Confrontation Clause-happy, they will rule that most lab reports are testimonial.  

If only from watching TV shows like "C.S.I.," most of us know that police agencies often rely on DNA analysis to identify the perpetrators of a crime. Of course, TV programs typically focus on bloody, violent crimes; how many viewers would tune in to watch police officers track down jaywalkers?

TV images notwithstanding, in everyday life property crimes such as burglary are far more prevalent than violent ones. The good news, according to a report funded and recently released by the National Institute of Justice (NIJ), is that DNA analysis can also be an effective tool for solving  property crimes.

The NIJ study focused on 5 different police agencies and compared the results of burglary investigations that used only traditional police practices like fingerprint comparisons with the results of investigations in which the agencies also collected and analyzed DNA evidence. DNA emerged as the big winner. For example, when police agencies relied only on traditional methods of investigation, they identified the perpetrators in only 12% of the cases. When they also used DNA analysis, the agencies were able to identify perpetrators in 31% of the cases.

Part of the study's good news was that police officers were just as good at collecting evidence suitable for DNA analysis as forensic technicians. This means that police agencies thinking about expanding the use of DNA analysis to burglary may not have to spend as much money on white lab jackets as they feared.

Nevertheless, the obstacles to using DNA evidence to solve property crimes are considerable. Existing forensic laboratories aren't sufficiently funded to meet the demands for DNA analysis that have already been placed on them. For example, the LAPD has acknowledged that it has a massive backlog of unexamined DNA evidence from violent crimes and that it was uncertain of its ability to find the funding needed to reduce the backlog. And DNA analysis isn't cheap. According to the NIJ report, the average cost of using DNA analysis to arrest burglars who would not have been arrested through the use of traditional police methods was $14,169 per case.

Unless governments are willing to make huge increases in police agency budgets, any use of DNA analysis to solve property crimes will mean a reduction in the use of DNA analysis to solve violent crimes. Thus, while the report's findings were impressive, there's little likelihood that DNA analysis will become a major tool for solving property crimes anytime soon.

Forensic testimony based on fingerprint comparison is a familiar part of many criminal trials. Based on the generally-accepted principle that no two people (even twins) have identical fingerprints, experts often tie suspects to crimes through providing testimony that the suspect's fingerprint matches the prints found at a crime scene.

Now, with the help of a new laboratory technique, forensic experts may be able to "read" fingerprints and identify substances embedded in them. The laboratory technique consists of a process called "mass spectrometry," and as a result, fingerprints may serve as suspects' "chemical signatures".  For example, an expert may be able to testify that "the person who left this fingerprint had been touching cocaine (or a poison, or an explosive)."  Such testimony would do more than tie a suspect to a crime scene: It would also help to explain the suspect's motive for being at the scene. For instance, assume that Bob is charged with murder-by-poison. At trial, forensic expert testifies, "I found traces of the same poison in fingerprints found at the crime scene, and in my opinion, the fingerprints are identical to those of Bob." Such testimony does more than prove that Bob was at the crime scene -- it also helps to show how Bob committed the murder.

Because of popular TV crime shows, such as C.S.I., jurors have generally come to expect and be favorably impressed with forensic evidence. "Smart" fingerprints, which may indicate not only who was at a crime scene but also their purpose for being there, is a potentially powerful prosecutorial tool.