Under the Microscope – Kevin Cheng
Reproducibility is one of the main principles of the scientific method. Reproducibility in forensic DNA interpretation typically relates to the reported match statistic. The development of probabilistic genotyping (PG) solutions using semi-continuous and continuous models was partly in a response to intra and inter laboratory differences to improve reproducibility of the results. However, there are still […]
Mixture Interpretation in DNA Forensics – An Interview with Greg Hampikian
Greg Hampikian, Executive Director of the Idaho Innocence Project, discusses concerns he has with current mixture interpretation procedures, changes he’d like to see for the future, and thoughts on how to improve forensic science. Transcript: Laura: Hi, we’re here at ISHI 29, and we’re talking with Greg Hampikian. Greg, why don’t […]
DNA Mixtures: A Forensic Science Explainer
Everyone’s DNA is slightly different. Thirty-five years ago, when scientists invented a way to distill those differences into a DNA profile, they revolutionized forensic science. That profile—a sort of genetic fingerprint—gave investigators a new and extremely reliable tool for solving crimes. DNA profiling can be so powerful and has been used successfully in so […]
Preparing for Expert Witness Testimony on Probabilistic Genotyping
With approximately half the forensic laboratories in the United States either using a probabilistic genotyping system or in some stage of implementation, cases processed using this method are now making their way through the court systems. Additionally, probabilistic genotyping has been used at the international level for nearly a decade. As you (as a scientist) make […]
Courtroom Testimony for Probabilistic Genotyping
“Ladies and Gentleman of the Jury, Jane Doe’s DNA matches the DNA found on the handle of the knife; therefore, she touched the knife and used it to stab John Doe”. As much as prosecutors would like that statement to come out of our mouths, that is not the role of the DNA Analyst. We […]
Database Searching – Taking Mixtures Further than Ever Before
At The Institute of Environmental Science and Research (ESR) we receive approximately 2600 volume crime samples per year and conservatively it is estimated that approximately 45% of these are mixed. These mixtures range from profiles where it is relatively easy to resolve a DNA profile suitable to load onto the Crime Sample Database by conventional […]
Teaching Old and New Dogs Mixture Tricks of the Future
Most forensic DNA analysts old and new have worked with scientists throughout the past that still wax nostalgically about the silver staining years (or other DNA methods that pre-date many of us). Generally speaking, nearly all DNA training programs involve components of the ‘history of DNA’ that cover the methods that led us to where […]
From Training to Casework: Validating and Implementing Probabilistic Genotyping in the Laboratory
Validating and implementing new technology can often feel like a daunting task. At DNA Labs International (DLI), staying on the forefront of DNA testing is critical to being able to offer new techniques that may be able to obtain results for those previously unsolved cold cases. However, like other laboratories, resources such as personnel and […]
Probabilistic Genotyping: Magic Hat or Mixture Resolution Tool?
STRmix™ is an invaluable tool for resolving complex mixtures. Analysts are now able to make conclusions about samples that would previously have been reported as inconclusive, which in turn is leading to more crimes being solved. When the analysis is conducted properly, the results make sense based on the profile that we are analyzing with […]