Tag Archives: DNA evidence

Arrestee DNA – Supremes Decide

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Arrestee-DNA

 

The FBI’s national DNA database, the Combined DNA Index System Program, includes an Arrestee Index of DNA profiles of people arrested in states where local law allows the collection of samples. The procedure of collecting DNA from arrestees has provoked longstanding debates. The US Supreme Court ended the debates with their June 3, 2013, approval of the controversial practice in a 4-3 decision.

The case Maryland v. King began in 2009 with the arrest of King for first- and second-degree assault charges in a Maryland facility. In compliance with the Maryland DNA Collection Act (MDCA), personnel took a cheek swab from King to generate a DNA profile. After King’s DNA profile matched the profile of DNA recovered during an investigation of an unsolved 2003 rape, King was charged with that crime. At his trial, King tried to suppress the DNA match, arguing that the MDCA was unconstitutional, because it violated the Fourth Amendment. The judge was not persuaded, and King was convicted of rape. The Maryland Court of Appeals set aside the conviction on the grounds that the parts of the law that authorized DNA collection from felony arrestees is unconstitutional. The State of Maryland appealed the decision to the Supreme Court.

The Supremes reversed the Maryland Court of Appeals. Four justices decided the following:

 DNA identification of arrestees is a reasonable search that can be considered part of a routine booking procedure. When officers make an arrest supported by probable cause to hold for a serious offense and they bring the suspect to the station to be detained in custody, taking and analyzing a cheek swab of the arrestee’s DNA is, like fingerprinting and photographing, a legitimate police booking procedure that is reasonable under the Fourth Amendment.

The opinion is worth reading not only for the brief history of methods used to identify criminals, but also for the dissent. As a preview, the dissenting Justice Scalia wrote: “The Court’s assertion that DNA is being taken, not to solve crimes, but to identify those in the State’s custody, taxes the credulity of the credulous.”

 

DNA – Fast

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DNA

 

Those multitasking, gun-toting TV CSIs perform DNA tests at record-breaking speeds. After all, they need to solve a crime in 44 minutes (allowing for commercials). The speed of real DNA analysis is catching up.

IntegenX® (Pleasanton, CA) has introduced its RapidHIT 200, which enables investigators to run a DNA test in a quick 90 minutes. The portable RapidHIT 200 is about the size of a small copy machine, and it analyzes DNA in a cheek swab. The device will allow law enforcement officers to quickly identify genuine suspects and eliminate people unrelated to the criminal activity.

“You’re going to see it in the field more,” said Jay Henry, laboratory director for the Bureau of Forensic Services (Salt Lake City). “The crime lab will be the crime scene. You can find out a lot more at the crime scene itself.”

The IntegenX website provides details about this technology, including a link to a recent Evidence Technology Magazine article highlighting RapidHIT.

 

Unraveling DNA Mixtures

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DNA mixture

 

The New York Times’ Liz Robbins recently reported a development in forensic DNA analysis. Over the past several decades, improvements in synthesizing DNA from trace amounts greatly increased the sensitivity of DNA profiling. Yet increasing sensitivity does not provide a solution to cases in which evidence contains trace amounts of DNA from several people.

Theresa A. Caragine and Adele A. Mitchell of the New York City medical examiner office’s forensic biology lab may have a solution. Their Forensic Statistical Tool is an algorithm for a software program that enables analysis of a DNA mixture uncovered from a crime scene and determines the probability that the DNA brew includes a defendant’s DNA profile.

Before judges allow results of the technology in court, the technique must survive Frye hearings. A Frye hearing is a challenge to the general scientific acceptance of new technology. Several Frye hearings are scheduled in New York courts.

Bacterial DNA Profiling

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 Finding DNA

Earlier this month, researchers at Washington University School of Medicine (St. Louis) and at the European Molecular Biology Laboratory (Heidelberg, Germany) reported a new type of DNA profile: DNA profiles from human gut bacteria. The researchers analyzed microbial DNA in 252 stool samples from 207 individuals, focusing on 101 species of microbes commonly found in the intestine. They found many types of DNA differences, the sort of differences that generate unique DNA profiles. For 43 subjects, the researchers collected two stool samples one month to six months apart. The scientists found little variability in the microbial DNA. In short, they discovered variability in DNA profiles between subjects and consistency in DNA profiles in subjects over time.

“The microbial DNA in the intestine is remarkably stable, like a fingerprint,” said George Weinstock, associate director of The Genome Institute at Washington University. “Even after a year, we could still distinguish individuals by the genetic signature of their microbial DNA.”

It’s not immediately obvious how this discovery could be incorporated into a crime story. But, if you can do it, then consider yourself on the cutting edge.

A more apparent application of bacterial DNA profiling to mystery stories is found in the discoveries of Noah Fierer and his colleagues at the University of Colorado in Boulder. They found that a typical human hand shelters about 150 species of bacteria. The types of bacteria living on skin vary greatly. In a 2008 study, they identified more than 4,700 different bacteria species living on the hands of 51 people. Yet only five species lived on the skin of every participant of the study.

In 2010, the researchers reported that computer users leave DNA traces of bacteria on computer mice and keyboards. These DNA traces more closely match the DNA of bacterial colonies that inhabit the hands of the individual who used the computer, compared with bacterial DNA traces of randomly selected people. The researchers obtained useful samples of bacterial DNA two weeks after a person touched computer equipment.