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DNA: Evolving Technology

DNA technology continues to move ahead.

February 01, 2003  |  by POLICE Staff

DNA testing is a complicated thing. But it's nowhere near as complicated as it used to be. Back in the earliest days of the technology in the late 1980s, DNA scientists would manually collect a sample from a molecule, then divide that sample into segments. These segments would be treated with enzymes then arranged by size and marked with probes before being exposed on X-ray film. When two samples matched, the likelihood was that they came from the same source.

The X-ray film DNA matching technique is known as Restriction Fragment Length Polymorphism (RFLP), and it was both labor intensive and time consuming, with testing procedures taking upwards of 12 weeks. It was also quite expensive.

Today, robotics and computerized Short Tandem Repeat (STR) technology have replaced much of the hands-on work in DNA testing to a point where complete testing may be done inexpensively and within a matter of days. The black bars that once characterized the "DNA signature" have been replaced by charts that more closely resemble EKG graphs, with their spiking peaks and valleys.

The Straw Man

Officers may only be limited by their imagination in their ability to exploit DNA-testing. For example, to capture a serial rapist, investigators with the Brea (Calif.) Police Department invited their prime suspect out to lunch.

What their "date" didn't know was that the people waiting on them in Taco Bell uniforms were actually officers. At one point, the suspect asked to have his drink refilled. The "employees" were only too happy to oblige, as they were able to retain his used straw for DNA testing while replacing it with another.

Although the defense predictably moved for suppression of the evidence, the court ruled in the prosecution's favor, noting that disposables such as straws are almost always discarded by their users.

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