Tag Archives: DNA

DNA – Fast

Posted on by

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.

 

Snacking with Conviction

Posted on by

Food behind bars

 

When criminals snack at a crime scene, they leave evidence behind. A bitemark in half-eaten food is one type of evidence. Peckish criminals also leave DNA and fingerprints.

Last week, Ryan Pfeil of the Medford Mail Tribune (Oregon) reported that burglary is a thirsty business. Burglars broke into a house through a garage and stole a flat-screen television, jewelry, and other valuable items. The burglars also took a container of orange juice from the refrigerator, drank from it, and left the container in the garage on their way out. Investigators sent the container to the Oregon State Crime Lab for tests.

Lab techs found DNA and fingerprints on the carton. They also found a match between one DNA sample and a DNA profile in the FBI database. The DNA match led investigators to a 33-year-old man who faces charges of first-degree theft, aggravated theft and burglary.

Around the same time, forensic scientists at the University of Abertay Dunde (Scotland) announced that they recovered latent fingerprints from foods.

“Although there are proven techniques to recover fingerprints from many different surfaces these days, there are some surfaces that remain elusive, such as feathers, human skin, and animal skin,” former crime scene examiner Dennis Gentles explained. “Foods such as fruits and vegetables used to be in that category, because their surfaces vary so much – not just in their color and texture, but in their porosity as well. These factors made recovering fingerprints problematic because some techniques, for example, work on porous surfaces while others only work on non-porous surfaces.”

University scientists overcame the problem by modifying a technique designed to recover fingerprints from the sticky side of adhesive tape. You can learn more about this breakthrough at the Abertay University website.

 

DNA and Killer Twins

Posted on by

DNA

 

A criminal who has an identical twin poses a problem: Identical twins arise from identical DNA. The microenvironment of a developing embryo affects the formation of fingerprint patterns. As a result, identical twins (who developed in different microenvironments) have different fingerprints. What happens when a savvy criminal does not leave fingerprints at a crime scene?

Barry Starr of QUEST Northern California tackled this question in his posting entitled, “Genetic Sleuthing, or How to Catch the Right Identical Twin Criminal.” Starr highlights a sexual assault case in Marseille, France. Using video evidence and standard DNA analyses, police identified two suspects who are identical twins. Which twin is the guilty one?

DNA can offer one way to distinguish between a set of identical twins. Twins begin life with identical DNA, but DNA changes. One type of change is called an epigenetic change. “Epigenetic” refers to changes in DNA that affect gene activity without altering nucleotide sequences in DNA. Researchers have found different epigenetic markers in the DNA of identical twins. DNA mutations, caused by chemicals and UV light, also cause small changes in DNA. Why didn’t police in Marseille rush to order DNA tests for epigenetic markers and mutations? The cost of one million euros to perform the tests discouraged that approach.

If you’re planning to include a killer twin in your story, peruse the comments to Starr’s article. You’ll find plenty of ideas about how your investigators might tackle the problem.

Unraveling DNA Mixtures

Posted on by

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.