Home DNA Testing

Home DNA Testing

News and insights in the world of DNA and genetics for paternity, immigration and forensics

Archive for October, 2011 Monthly Archives

I just came across an article distributed by the National Public Radio (NPR) about a scientific beak though in DNA sequencing. This article just goes to show that DNA can answer current question about crimes, relationships and health but it can also help us look into our past.

Scientists have used DNA lurking inside the teeth of medieval Black Death victims to figure out the entire genetic code of the deadly bacterium that swept across Europe more than 600 years ago, killing an estimated half of the population…

People back then had no access to modern antibiotics and were likely weakened by other infections as well.

Poinar says the ancient Black Death DNA looks so similar to Yersinia pestis that still infects people today that researchers believe the medieval strain must be the ancestor of all modern strains.

The Natural History Museum of Denmark’s Thomas Gilbert says the insights that come from these studies will be of interest not only from a historical perspective, but also to help scientists understand how deadly epidemics have emerged in the past so that they can get ready for what might come in the future.

For the full story see: Decoded DNA Reveals Details Of Black Death

While this field of research might not seem very practical at first glance there is a wealth of knowledge about, diseases, bacteria and the ways we interact with them and how they spread and change.

By now you have heard the news: On October 3rd, 2011, Amanda Knox and former boyfriend, Raffaele Sollecito, won their appeal in an Italian court and were acquitted and freed for the murder of British student, Meredith Kercher. Despite a previous trial and guilty verdict based on supposed DNA evidence, both convicted parties won an appeal and a deeper trial over the evidence occurred.

While we could pick over all of the details of the case, we’ll leave that for another organization to discuss. Instead, allow us to focus alone on genetic evidence.

With no obvious motive, no independent witnesses and no confessions, the Italian prosecutors had to rely on genetic evidence found at the crime scene to convict Knox and Sollecito. This makes sense as genetic evidence is supposed to be iron clad.  Or is it?

The original conviction relied on traces of Sollecito’s DNA being found on the victim’s (Kercher) brassiere clasp, together with traces of DNA from both defendants being found on the knife allegedly used to slash Kercher’s throat. However, similar to our famous U.S. tales of botched crime scene evidence (ie. the Jon Benet Ramsey or OJ Simpson cases), the prosecutions evidence has been marred with rumors of bad police work and possible fabricated evidence. Furthermore, not only did the defendants know Meredith Kercher, but Amanda Knox lived with her.This complicates matters on an enormous level.

The first issue is called “contamination”. Unlike crimes where the victim and perpetrator don’t know each other, and therefore a genetic link is most likely an obvious connection, it is hard to do the same with roommates and their visiting friends – there will always be matching DNA present. And although DNA evidence puts a person ‘at the scene of the crime’; it does not necessarily prove they committed the crime.

Secondly, although DNA evidence can match the scene of a crime, it does not allow for “time-based evidence”. There is no telling if a match occurs because a victim or perpetrator was present at the time of the incident or exists because they were present at some other point in history.

Finally, although many people have been successfully prosecuted on DNA evidence, it is not failsafe or full proof. Typically, a DNA sample found on a murder weapon will be said to match the DNA of the suspect to the extent that only one person in one million would have the same profile. However, if a particular genetic profile is held by one person in, say, one million this means that in a country with a population of 60m will have 60 people that give a perfect mach for the DNA evidence and even more would match a partial profile of that evidence.

In the U.S., a man called Kerry Robinson was convicted a few years ago of gang rape. In an independent investigation last year DNA evidence from the crime scene plus Robinson’s DNA profile was shown to 17 ‘blind’ analysts with no contextual information: the 17 experts were hugely divided – 12 said the suspect could be excluded.

Although no one can or should doubt the genetic evidence is a powerful tool for solving crime, it is not perfect and it has it’s weakness, from false positives to human error.  One thing is for certain – this legal matter and it’s evidence will be scrutinized for a long time to come. Let’s hope that we can learn from it.

 

 

Read more: http://www.dailymail.co.uk/debate/article-2044935/As-Amanda-Knox-walks-free-DNA-evidence-trial.html#ixzz1ZlPcRlgY