I have always wondered at the reliability of DNA evidence used in Australian courts. This type of evidence has gained an almost ''wonderous'' and exhalted level of acceptance. Why?
There is growing concern on the ''other side'' that DNA evidence is not as reliable as you think. I'm just a layman, I'm not a lab technician or a scientific brain, but I have trawled as much of the information as I can that is available to me, and I have no reason to believe that it is wrong. I have presented some of that information here.
Only 1000! ... to me, in an Australian court, you could not convict someone solely on DNA evidence if there is a possibility that one of the other 999 people could have committed that crime. Surely a judge or jury could not reasonably believe this is fair? But it happens.
There is growing concern on the ''other side'' that DNA evidence is not as reliable as you think. I'm just a layman, I'm not a lab technician or a scientific brain, but I have trawled as much of the information as I can that is available to me, and I have no reason to believe that it is wrong. I have presented some of that information here.
Generally, DNA is 99.9% reliable. In practical terms, in a city of 1 million people, if a person commits a crime and is identified using DNA, only 1000 other people could have committed the crime.
Only 1000! ... to me, in an Australian court, you could not convict someone solely on DNA evidence if there is a possibility that one of the other 999 people could have committed that crime. Surely a judge or jury could not reasonably believe this is fair? But it happens.
Despite popular belief, DNA evidence is not as accurate as people might assume. The 99.9% people often cite is actually just an estimate and no one is actually sure how accurate it might be. While every person's DNA is different, a DNA profile, the bit used as evidence, is only a small sliver of a person's entire DNA, and even siblings may share a very similar DNA profile. In 2001 Kathryn Troyer ran a test of Arizona's DNA database of felons and discovered two felons with DNA profiles where 9 of 13 markers were identical, despite the fact that one was white and one was black, and later discovered dozens of other similar matches, yet the FBI estimates the odds of some one sharing those genetic markers to be 1 in 113 billion. As word spread, these findings by a little-known lab worker raised questions about the accuracy of the FBI's DNA statistics and ignited a legal fight over whether the nation's genetic databases ought to be opened to wider scrutiny.
The FBI laboratory, which administers the national DNA database system, tried to stop distribution of Troyer's results and began an aggressive behind-the-scenes campaign to block similar searches elsewhere, even those ordered by courts, a Times investigation found.
At stake is the credibility of the compelling odds often cited in DNA cases, which can suggest an all but certain link between a suspect and a crime scene.
When DNA from such clues as blood or skin cells matches a suspect's genetic profile, it can seal his fate with a jury, even in the absence of other evidence. As questions arise about the reliability of ballistic, bite-mark and even fingerprint analysis, genetic evidence has emerged as the forensic gold standard, often portrayed in courtrooms as unassailable.
But DNA "matches" are not always what they appear to be. Although a person's genetic makeup is unique, his genetic profile -- just a tiny sliver of the full genome -- may not be. Siblings often share genetic markers at several locations, and even unrelated people can share some by coincidence.
No one knows precisely how rare DNA profiles are. The odds presented in court are the FBI's best estimates. The fact that only 13 markers are used out of the entire DNA strain should bring into question the validity of DNA evidence.
You have to ask the question. If the FBI were so confident of the DNA testing model and the accuracy of said model, why did they try and stop the publication of Troyers results and try and block similar searches and scrutiny of the CODIS database? To me, this is a key point. One could take the position that maybe they don't want the ''general public'' to know too much about DNA testing techniques and want to keep it shrouded in mystery. This would help to keep the ''god-like'' status of DNA evidence alive and well in courts, and no doubt, obtain more convictions. Who cares if the defendant is guilty or not, the DNA evidence says they are, so they must be.
Law enforcement officials and prosecuting attorneys are quick to identify the benefits of DNA evidence for the criminal justice system. DNA evidence, they argue, is even more useful than fingerprinting, with several advantages over that more traditional tool of investigation. DNA evidence is more readily available in criminal investigations than are legible fingerprints because body fluids and hair are more likely to be left at the scene of a crime. DNA evidence is also "robust"; that is, it does not decay or disappear over time. The DNA in a piece of physical evidence such as a hair may be examined years after a crime. Proponents of DNA evidence fear that successful courtroom attacks on its reliability will erode public confidence in its use, giving the state less power in bringing criminals to justice. Defense attorneys and others who are skeptical about DNA evidence strongly disagree with many of these claims. While generally accepting the scientific theory behind DNA evidence, including its ability to exculpate the innocent suspect, they assert that it is not nearly as reliable in practice as its proponents claim. They argue that DNA evidence may be unreliable for any number of reasons, including contamination owing to improper police procedures and faulty laboratory work that may produce incorrect results.
Barry C. Scheck is a leading critic of DNA evidence. A professor at the Benjamin N. Cardozo School of Law, a defense attorney in several notable cases involving DNA evidence, and an expert for the defense in the celebrated 1995 murder trial of O. J. Simpson, Scheck has led the movement for increased scrutiny of DNA evidence. Conceding that "there is no scientific dispute about the validity of the general principles underlying DNA evidence," he nevertheless argued that serious problems with DNA evidence remained. He found particular fault in the work of forensic laboratories and pointed to research that showed that as many as one to four percent of the DNA matches produced by laboratories were in error. Laboratories denied such claims.
Scheck also criticized the procedures used by laboratories to estimate the likelihood of a DNA match. Because juries consider the probabilities generated by the labs—figures such as one in 300 million or one in 5 million—when assessing the validity of DNA results, it is important to ensure that they are accurate.
DNA critics assert that statistical estimates of a match may be skewed by incorrect assumptions about the genetic variation across a population. In some population subgroups, they claim, individuals may be so genetically similar that a DNA match is more likely to occur when comparing samples drawn from within that subgroup. Examples of such subgroups are geographically isolated populations or tightly knit immigrant or religious communities. Other problems may occur in cases where suspects are closely related to one another. Critics call for more research on population substructures and DNA similarities within them, in order to get a better understanding of statistical properties.
As more and more cases go before courts based soley on DNA evidence, one must also consider another side benefit to the police force. It's cheaper (to put together a prosecution case). No more mucking around with grass seeds stuck to the bottom of shoes, no more fingerprints. Find one hair belonging to the accused, and you will have a case. And if the courts and prosecution have their way, the DNA evidence will surely point to the guilt of said accused.
Barry C. Scheck is a leading critic of DNA evidence. A professor at the Benjamin N. Cardozo School of Law, a defense attorney in several notable cases involving DNA evidence, and an expert for the defense in the celebrated 1995 murder trial of O. J. Simpson, Scheck has led the movement for increased scrutiny of DNA evidence. Conceding that "there is no scientific dispute about the validity of the general principles underlying DNA evidence," he nevertheless argued that serious problems with DNA evidence remained. He found particular fault in the work of forensic laboratories and pointed to research that showed that as many as one to four percent of the DNA matches produced by laboratories were in error. Laboratories denied such claims.
Scheck also criticized the procedures used by laboratories to estimate the likelihood of a DNA match. Because juries consider the probabilities generated by the labs—figures such as one in 300 million or one in 5 million—when assessing the validity of DNA results, it is important to ensure that they are accurate.
DNA critics assert that statistical estimates of a match may be skewed by incorrect assumptions about the genetic variation across a population. In some population subgroups, they claim, individuals may be so genetically similar that a DNA match is more likely to occur when comparing samples drawn from within that subgroup. Examples of such subgroups are geographically isolated populations or tightly knit immigrant or religious communities. Other problems may occur in cases where suspects are closely related to one another. Critics call for more research on population substructures and DNA similarities within them, in order to get a better understanding of statistical properties.
Promoters of forensic DNA testing have done a good job selling the public, and even many criminal defense lawyers, on the idea that DNA tests provide a unique and infallible identification. DNA evidence has sent thousands of people to prison and, in recent years, has played a vital role in exonerating men who were falsely convicted. Even former critics of DNA testing, like Barry Scheck, are widely quoted attesting to the reliability of the DNA evidence in their cases. It is easy to assume that any past problems with DNA evidence have been worked out and that the tests are now unassailable.
The problem with this assumption is that it ignores case-to-case variations in the nature and quality of DNA evidence. Although DNA technology has indeed improved since it was first used just 15 years ago, and the tests have the potential to produce powerful and convincing results, that potential is not realized in every case. Even when the reliability and admissibility of the underlying test is well established, there is no guarantee that a test will produce reliable results every time it is used. In our experience there often are case-specific issues and problems that greatly affect the quality and relevance of DNA test results. In those situations, DNA evidence is far less probative than it might initially appear. The criminal justice system presently does a poor job of distinguishing unassailably powerful DNA evidence from weak, misleading DNA evidence.
The problem with this assumption is that it ignores case-to-case variations in the nature and quality of DNA evidence. Although DNA technology has indeed improved since it was first used just 15 years ago, and the tests have the potential to produce powerful and convincing results, that potential is not realized in every case. Even when the reliability and admissibility of the underlying test is well established, there is no guarantee that a test will produce reliable results every time it is used. In our experience there often are case-specific issues and problems that greatly affect the quality and relevance of DNA test results. In those situations, DNA evidence is far less probative than it might initially appear. The criminal justice system presently does a poor job of distinguishing unassailably powerful DNA evidence from weak, misleading DNA evidence.
http://www.bioforensics.com/articles/champion1/champion1.html
The link above will take you to a page with diagrams, graphs and the like explaining how some DNA labs show their results. It gives defence lawyers an opportunity to look at results and see how a DNA lab has conveniently ''ignored'' a couple of ''loci'' which could be all the difference in a person being found guilty or not guilty.
Imagine the scenario in 10 or so years time, that DNA evidence is found to be not as accurate as first thought. What does the government do? If it allows publication of said results, it leaves itself liable to hundreds of million of dollars in compensation to criminals convicted using DNA. Cases would have to be overturned. Convictions quashed. It would be an absolute nightmare for the police, courts and government. That's if the public finds out. If the public doesn't find out, all will be good. I wonder what they'd do? It lends some weight as to why the FBI fought feverishly to stop the publication of Kathryn Troyers results in the USA.
They thought Thalidomide was the new wonder drug... until.....they found out the hard way. I'd hate to think that was the way with DNA testing.
To all those people who will over time, be called to jury service, don't just believe the first thing you hear - question it. Don't just blindly believe what the prosecution and court tell you. The prosecution want one result, Guilty. The jury is there to guard against bias or vindictiveness on the the part of the prosecution and judiciary. Such apparent contradictions lead to a great deal of pressure to abandon the jury system. It would be a great loss. Don't just take it at face value if DNA evidence is used.
Get Real
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