January 25, 2001
 
 

DNA Detective

Christopher Ochoa is found innocent
When the results of DNA tests recently freed Christopher Ochoa after he spent 12 years in a Texas prison, he became the latest of almost a hundred prisoners whom genetic evidence cleared of serious crime charges, not to mention the hundreds of suspects who have been exonerated. 

As the technology continues to advance, forensic scientists and legal experts alike are turning to this powerful biological tool more than ever before.

Genetic blueprints

Ochoa had an emotional reunion with his mother after his long stay in prison, but Frank Lee Smith wasnít as fortunate. Smith died of cancer in prison early last year after spending 14 years on death row for the rape and murder of a little girl. Last month, however, DNA tests showed he didnít commit the crime.
 

Although the testing was done too late to save Smith, the forensic scientists who perform DNA tests say their work can be gratifying. "One of the more satisfying things we do is to prove that someone whoís been suspected or even arrested of a crime has not actually committed that crime," says Robert Shaler, director of the New York City Forensic Biology Laboratory.

It used to be that forensic experts had to rely on fingerprints to place suspects at crime scenes. DNA is like a fingerprint, in that everyoneís is unique, but itís also much more precise. "Fingerprints are found at crime scenes all over the country but a vast majority of them are unusable, whereas a single molecule of DNA potentially can be used to identify an individual," says Shaler.

A genetic blueprint of who we are, DNA can be isolated from a variety of materials, including blood, bone, saliva, semen, and hair. Experts begin by isolating the DNA from samples found at the crime scene and determining how much of it there is. 


The identical DNA bands seen in
the three lanes on the right are 
from one person while the bands 
in the three lanes on the left are 
from a second individual.
DNA testing can be applied in a variety of ways. "One is to take a crime scene sample and compare it to another crime scene sample and show that that particular crime was committed by the same person," says Shaler. His laboratory has also matched samples with the DNA of arrested suspects who are on trial, as well as those already incarcerated.

But those with the most to gain from DNA testing are the more than 3,000 people on death row. Smith would have been the tenth person facing the death penalty to be exonerated based on DNA evidence, which has only been used since the early 90ís.


Robert Shaler and his lab 
technician work with DNA samples.
Opponents of the death penalty question why the test isnít used more often. "The cost of having the death penalty is absolutely enormous and the cost of the DNA test is not particularly high, and falling," says Eric Freedman, a law professor at Hofstra University Law School. "And of course, if somebody is released, then the state has no cost whatsoever." 

During the presidential campaign, George W. Bush said he supported DNA testing if it can confirm guilt or innocence in a death penalty case. But New York and Illinois are the only two states where death row inmates have a right to DNA testing.

Freedman points out that DNA testing is not a panacea. "It is an ability to get a window on the accuracy of the criminal justice system in a small category of cases where biological evidence exists," he says. But to those accused or convicted of crimes, this scientific tool could make or break their cases. For some, it could even prove to be a matter of life or death.




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