The postponement was related to several issues, including new evidence being submitted in the case in recent weeks and the prosecution’s desire to try the officers in a specific order. The state this month said it intended to use DNA evidence in the cases, causing defense attorneys to submit requests for additional information as to the collection, storage and application of that evidence in their clients’ cases.

It is difficult indeed to imagine what Mosby and her deputies could be thinking. DNA evidence is almost exclusively useful as a means of unquestionably placing a criminal suspect at the scene of a crime. In some cases, its presence can wipe away alibis sworn by 100 witnesses. But there are limits.

In a rape case, for example, DNA would be useful primarily in establishing the presence of a suspect only if the encounter was not consensual. If both parties agree there was intimate contact, but disagree on the permissions involved, there is no point in using DNA, because there is no need to prove the suspect was present or that they had intimate contact with the victim. If the suspect’s identify was unknown, however, DNA could positively identify a suspect–if and when one were developed.

The problem is there is no doubt that the officers were present, when and where. One possibility is that the prosecution intends to try to impeach an officer’s statement. Say an officer claimed not to have entered the van, yet a trace of their DNA was found in it or on Gray or a trace of Gray’s DNA was found on them. Got ‘em! Right?

Unfortunately, no. There are many ways for DNA to be transferred from person to person, from object to object and from person to object. An officer’s hair or even shed skin cells could fall onto someone they didn’t actually touch and end up somewhere they had never been. But in this case, any one of those officers could have been inside that van prior to, or after, meeting Gray. A transfer could occur merely by an officer brushing a portion of the van Gray had brushed. An officer, like Porter, that actually handled Gray could also brush against an officer that had not handled him and transfer DNA traces.

DNA is far less useful and definitive than portrayed on TV CSI shows, which is also the case with fingerprints. There is no massive central registry for either that would allow the police to input a sample or a print and have an all-powerful computer spit out a precise match with a bad guy’s complete record and current address. To use either, it must generally be compared with a known suspect, and it is useful only if there is no reasonable explanation for finding the suspect’s DNA at the scene of the crime. That won’t be the case here.

On the September 29 edition of The Kelly File (Fox), there was some discussion that Mosby intends to use DNA to establish that there was blood–presumably Gray’s–on Goodson’s uniform. Again, this is a fool’s errand. Goodson need not have directly touched Gray to get blood on his uniform. I wish I had a dollar for every time I ended up with the blood of suspects/arrestees on my uniform–or skin–to say nothing of trace DNA evidence. I shudder to think of how much of that ended up in my bathroom, my closet with my daily clothing, my personal vehicle, etc.

One possibility, however, is that the prosecution is planning to use such “evidence” as a smokescreen to try to confuse a jury conditioned to believe the magical fiction of CSI. Or possibly, they plan to introduce misleading or even false evidence in an attempt to trick officers into testifying, potentially giving them a chance for a dramatic Perry Mason interrogation on the stand. The prosecution would surely love to have any officer testify, in the hope of getting any statement they might possibly be able to use against the other officers.

It’s possible that there is some significant evidentiary issue involving DNA in this case, as difficult at this point as it may be to imagine what it could be. It’s more possible that as with the Terry ruling, Marilyn Mosby has no idea of the law, or is willing to ignore or warp it in the pursuit of social justice.