You do not need a degree in biochemistry to get the gist of forensic DNA. Everyone gets the fact that DNA is unique to each human being, and can be used to connect a perpetrator to a crime. The first crime solved by the analysis of DNA was in 1988 in England when Colin Pitchfork was convicted of murder, thanks to the efforts of Alec Jeffreys. We've come a long way, baby. New developments in DNA forensics are both remarkable and frightening. We'll start with what is remarkable.
Twins have caused investigators headaches since the beginnings of criminal investigation. Eyewitnesses could give a description of an offender, but that description still left doubt when twins were involved. When DNA technology became available, it worked well in standard crimes, but it was useless in crimes where one of a set of identical twins was involved. Which twin was guilty? In Suffolk County, Massachusetts, twins Dwayne and Dwight McNair caused this age-old problem to surface. Two women were abducted and raped and the DNA evidence showed it was one of the two brothers. Circumstantial evidence pointed to Dwayne as the perpetrator. A new test called DNA methylation was used. Every cell you have contains all your DNA, but certain DNA is shutoff, and other DNA is turned on. The cells in your eye have the DNA for eye requirements turned on, but the DNA needed for hearing is turned off. These patterns of on and off DNA also occur for more subtle uses which are influenced by your environment. As twins age, the patterns of these on and off genes diverge. One twin may smoke or drink. The other may not. The DNA of each twin is chemically melted. They should have different melt temperatures, which can then be compared to the crime scene DNA melt temperature, identifying the correct twin. In this case, Dwayne was found to be two billion times more likely to have committed the crimes in question. The Prosector's request to use DNA methylation as evidence was rejected. Dwayne is currently in jail awaiting trial.
FDP or Forensic DNA Phenotype
Phenotypes are what make you look the way you do, and those traits are determined by genes. Several companies are now making claims that they can create a likeness of a perpetrator by analyzing those genes. The resulting picture looks like an avatar from a video game, but there are high hopes this will improve. So far, several cases have been solved using this technology, including a double murder in North Carolina using the pictures above. The company who achieved this, Parabon, is not giving up the algorithm they are using so that their results can be recreated. As it stands, we have very little information on which genes affect facial characteristics, but we can get approximate skin color, eye color, race, and sex from DNA. This research clearly has a long way to go, but as of right now, it can be pertinent in cold cases where there is DNA that cannot be matched in the DNA database or to suspects. It should only be used as a last resort when everything else falls through. These avatars may bring false hopes to the victim's families, and undue claims against innocent people who resemble them. Time and research will tell.
Skin Cells—It only takes one.
Touch DNA is exactly what it sounds like. Scientists can now process DNA from a single skin cell left behind by an offender, but also by the innocent. There are several well-known cases that have been impacted by this extremely sensitive DNA testing. It only takes one skin cell, and we drop thousands of them everywhere we go on everything we touch. The JonBenet Ramsey case was reopened in January 2017 based on touch DNA found on her panties that was shown not to be from her parents. They are assuming it has to be from the killer. But is it? DNA transfer not even associated with the crime in question has been causing problems. It has nothing to do with contamination in the lab doing the testing either. The "Phantom of Heilbronn" is a German case where female DNA was found in a crime scene sample. After years of looking for a female perpetrator for a series of murders, investigators discovered it was contamination that took place in the factory where the swabs were made. Then there is the case of a homeless man in California who was charged with the murder of a multimillionaire Silicon Valley man in his home. The homeless man had an alibi. He was in a coma in the hospital and under a 24-hour medical watch. His DNA had been transferred by paramedics who treated the wealthy victim three hours later. They used the same oxygen monitor on both men. These are cases that were high profile. No one was hurt by these errors, and only wasted the investigator's time. How many times will this kind of mistake happen with people of low priority? It is worrisome, and it will have repercussions in the criminal justice system. Perhaps there are people languishing in prison at this moment that didn't do the crime they were sentenced for. Maybe there are those who have gotten away with crimes because we didn't have it sooner. Therein lies the rub.