There are 3 billion (3,000,000,000) bases in my genome—in each of the cells of my body. Likewise, Johanna, the writer who sits next to me at work also has 3 billion bases in her genome. Furthermore, our genomes are 99% the same. Still, that’s a lot of places where my genome can differ from hers, certainly enough to distinguish her DNA from mine if we were both suspected of stealing cookies from the cookie jar. The power of discrimination is what makes genetic identity using DNA markers such a powerful crime solving tool.
The completion of the human genome project in 2003 ushered in a tremendously fast-paced era of genomics research and technology. Just like computers shrank from expensive, building-filling mainframes to powerful hand-held devices we now call mobile phones, genome sequencing has progressed from floor-to-ceiling capillary electrophoresis units filling an entire building to bench top sequencers sitting in a corner of a lab. The $99 genome is a reality, and it’s in the hands of every consumer willing to spit into a tube.
Commercial DNA sequencing services are promising everything from revealing your true ancestry to determining your likelihood to develop dementia or various cancers. Is this progress and promise or is it something more sinister?
Imagine being convicted of a crime for which you are not guilty—not some minor crime, but one of the most heinous crimes imaginable: the rape and murder of a young girl. Would you feel shock and anger at the injustice? Disappointment in the legal system that could make such a horrible error? Sadness and depression at the thought of spending time imprisoned for a crime that someone else committed? Probably all of those emotions and more. At your sentencing hearing, the situation gets worse; you are sentenced to death. Now, this horrible crime will prematurely claim the life of two innocents: the young girl and you.
In May of 1986, a woman in Orange County, Florida, was surprised by a man who entered her apartment and raped her at knifepoint. Despite the fact that she got a glimpse of his face, the chances of identifying and convicting her rapist were slim. Although law enforcement officers did their best to identify the perpetrator, their investigative techniques in the case were limited compared to our current set of forensic tools. That changed when Jeffrey Ashton, an assistant attorney for the state of Florida, saw an advertisement for DNA-based paternity testing in a magazine and began to wonder if DNA testing could also be used to identify the man responsible for the attack.
In an earlier blog entry, I wrote about the ill-fated Louis XVI, the French king who was famously beheaded along with his wife, Marie-Antoinette, during the French Revolution in 1793. Witnesses to the execution dipped handkerchiefs in the king’s blood and kept them as souvenirs of the common people’s rebellion. In 2010, scientists published the presumptive DNA profile of the king, obtained from one of these bloody handkerchiefs (1). Shortly after this profile was published, doubters surfaced, arguing that scientists could not say with certainty that the blood was that of Louis XVI. Clearly, more work was needed to identify the source of the blood. Recently, additional work was published (2,3). The most recent data (3) were presented at the International Symposium on Human Identification; these newest data cast doubt on the identification of the remains of not one king, but two.
As a society, we love our pets. In many cases, cats and dogs are our surrogate children. We spoil them with treats, toys and plenty of attention. They reward us with unconditional love (or as some cats seem to think, simply with their presence). However, in addition to the many joys of animal companionship, there are unpleasant effects and responsibilities associated with pet ownership. Cat or dog hair covers our furniture, our favorite sweater and every other possession, whether or not these items come into direct contact with our hairy friend. Some dogs have uncontrollable urges to chase cars or bark incessantly; cats often dispense fur balls randomly around the house or become a pest every time we use the can opener. One of the worst responsibilities, in my opinion, is cleaning up after them. Cats have litter boxes, which must be cleaned periodically, and dogs generate piles of yesterday’s dog food, which must be picked up. A responsible dog owner even carries plastic bags during walks to collect piles that Fido leaves along the way. However, not all pet owners are responsible enough to pick up the offending material, and this is causing problems in many communities. Some property owners are now implementing a high-tech solution to this unsightly problem: DNA testing. Continue reading “Another Application for DNA Testing: Getting the Scoop on Dog Poop”
The past few decades have seen amazing advances in forensic science that are instrumental in analyzing DNA evidence to put perpetrators of crimes behind bars and exonerate people convicted of crimes that they did not commit. [Read William Dillon’s story of wrongful conviction].
Unfortunately for some people, these techniques were developed too late. One of those people was Dr. Hawley Harvey Crippen, who was accused and convicted of killing his wife Cora in 1910 using the forensic techniques available at the time. Until the very day of his execution, Dr. Crippen insisted that he was innocent, and now there is strong DNA evidence to support his claim. Recently, forensic scientists from Michigan State University analyzed DNA evidence in this case and published their results in the Journal of Forensic Science (1): The human remains that were so instrumental in Dr. Crippen’s conviction were not those of his wife. Continue reading “Was Dr. Crippen Innocent After All? New Forensic Evidence 100 Years After his Execution”