Robert Jones

Many tools have been developed to aid law enforcement personnel. These include fingerprinting, blood typing, lie detecting and DNA (desoxyribonucleic acid) analysis. The latter, especially, has undergone continuing improvements and is now an established forensic tool. Its use has been spreading to law enforcement agencies throughout the world. Even a problem of needing a sizeable sample of a substance containing DNA for analysis has been solved by a Nobel-Prize-winning discovery of means for amplifying (replicating) quite small (even degraded) amounts of DNA. DNA is found in every nucleated cell in our bodies, and it is the same in every such cell. DNA analysis, sometimes referred to as DNA profiling or DNA fingerprinting, is basically a process that compares the genetic makeup of a small number of DNA segments in testable samples to reveal their presence or absence. There are a number of techniques used, and those that are least accurate are still capable of excluding innocent suspects. In the sense of this discussion, the success of DNA analysis is to be considered a first forensic PING.

Just as it appeared that DNA analysis was becoming regarded as a forensic gold standard, however, a nasty dose of aqua regia* (so called because it is sufficiently corrosive to dissolve “royal” metals such as gold and platinum) showered down upon it. Scientists dribbled the representative first drop of the shower by simply separating red and white blood cells and plasma in a female donor’s blood. Next, they took DNA from a male donor and added it to the female’s red blood cells, which contain no DNA. This created blood that contained only the DNA of the male. To test the deception, a sample was sent for profiling to a laboratory used by the FBI, where the resulting profile raised not one eyebrow. More drops were dribbled by fabricating saliva. Bucketfuls of aqua regia were dumped when scientists revealed that, if they had a DNA profile of a person, they could construct DNA to match it without having any tissue at all from that person. One could then plant the DNA at a crime scene to incriminate an innocent person. Just imagine what defense attorneys could do with that information. In the new sense of this discussion, the corroding of the forensic DNA gold standard may be considered a first forensic PONG.

Just when it appeared that the forensic DNA gold standard faced dissolution, a niobium umbrella descended to protect the gold standard from the aqua regia shower. This represented a development by scientists of a method that detected fabricated DNA. The method is based on the fact that amplified (replicated) DNA is not methylated (does not have certain molecules attached at specific points to the DNA). In the more recent sense of this discussion, the ability (represented by the niobium umbrella) to protect the forensic gold standard by performing a test for the presence or absence of methylation may be considered a second forensic PING.

Just as the forensic gold standard was apparently being restored, however, the niobium umbrella representing the method of detecting fabricated DNA was doused by concentrated sulfuric acid, which promptly began redissolving it. It was made public that any competent molecular biologist would know how to use a simple treatment** to methylate amplified DNA. This, of course, would severely reduce the usefulness of the methylation test. If this is true, such a treatment could certainly be considered a second forensic PONG.

Fortunately, DNA evidence is not the only type of evidence considered in investigations and trials.

Extra facts:

* Aqua regia, as we might recall from our chemistry classes, is an acid comprising a mixture of one part (by volume) concentrated nitric acid and three parts concentrated hydrochloric acid.

** For those biochemists among us, the simple treatment referred to is a CpG methyltransferase treatment, CpG standing for cytosine and quanine (no, not quinine) separated by a phosphate that links the two nucleosides in DNA.

The foregoing will not appear on the final exam.