A researcher from the University of Twente has devised a system for instantly locating the presence of human DNA at a crime scene.

Brigitte Bruijns, a graduate student at the Netherlands-based university, described the lab-on-a-chip system in as capable of quickly inspecting a crime scene for human DNA and determining whether the sample is enough to undergo additional testing in a laboratory.

Each year, hundreds of thousands of DNA analyses are conducted on samples, with half of the samples returning unusable DNA profiles. Valueless, time-consuming testing could be eliminated by the lab-on-a-chip technique. According to Bruijns, the lab-on-a-chip will offer clear 'yes' or 'no' answers. A 'no' means that investigators should look for trace samples elsewhere at the crime scene, while a 'yes' answer means that human DNA is present and thus should be taken to the lab for DNA profiling.

The lab-on-a-chip is a small device upon which Bruijns combined a number of laboratory techniques including sampling; DNA workup. where cells are broken down to reveal DNA; DNA amplification; detection of DNA; and DNA storage until laboratory analysis.

Although Bruijns acknowledges that devices already exist that carry out on-site testing, showing that a sample contains saliva, semen, urine or human blood, she explained that the lab-on-a-chip device accomplishes all of the steps leading up to detection in a closed-system design that reduces the risk of cross-contamination.

"This lab-on-a-chip is like a sort of pregnancy test," Bruijns said. "Forensic experts see a 'YES' or 'NO' within 30 minutes. The fact that half of all samples do not result in a human DNA profile, and are therefore worthless, is very frustrating for professionals in the forensic world. Investigating all the reasons for this would be a study in itself. Sampling requires more study. Many samples contain little DNA and the probability of achieving a good profile is closely related to the quantity of DNA you have. The sample may be damaged, for example, if it is very hot and humid or if the sample is exposed to a lot of UV light."

A digital version of Bruijns' Ph.D thesis, "Microfluidic devices for presumptive forensic tests," is available upon request at the University of Twente website.

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