Just what is the impression of forensic science held by members of the general public (our pool of jurors)? If they believe everything they see on TV or in the movies, they are being sadly misled. Our local attorneys believe that, at the very least they have been generally misinformed about the likelihood of finding fingerprints by exposure to the media. Because of this I will be in court in the coming weeks giving testimony on the difficulties of recovering fingerprints from duct tape… Of course the same attorney moments later mentioned how unusual it is to recover fingerprints from guns- Which he felt had good surfaces for recovering fingerprints. (I re-educated him on this point, as guns have generally lousy surfaces, not to mention all the handling involved in firing/recovering/and making safe prior to processing).
It has been my experience that not only do members of the general public have a lack of understanding of forensic science, but that police officers, detectives, prosecutors and judges are often not much better. I think this trend is likely to continue as long as forensics is misrepresented in the media. People tend to refer to personal experience when assessing the value of new information, and when the personal experience with forensic science is “I was watching Law and Order on TV the other night and they…. “
I was watching Law and Order on TV the other night and here’s what happened: Detectives track down a suspect from whom they have a court order to draw a blood sample. Suspect’s attorney manages somehow to get it set aside as an invasion of privacy. Detectives decide (and I can see them doing this) that well, he had a cut on his hand so lets go get in his garbage where he has no expectation of privacy (which is true) and get the band-aid he had on his finger to use as a reference sample. I got a chuckle out of this as I knew perfectly well that you’re going to be hard pressed to find a lab to even test this and compare it to the crime scene samples, and even if you do, what do you have? You have a match of 2 unknown samples. Provided of course that you found the right band-aid, and that being wadded up in a steamy dumpster for a couple of days didn’t degrade the sample beyond use. I explained this to my wife, who understood right away why you don’t use an unknown to match with an unknown and expect the results to mean anything. At this point I had to leave the room for a few minutes. When I got back my wife said, “You’re not gonna believe this: not only did they match the bloodstains, but they found the suspect’s fingerprint on the band-aid.” I rolled on the floor laughing.
Could we recover a fingerprint from a band-aid? Yes. Could we get a workable blood sample from a band-aid? Yes. Even after being in a steamy dumpster for a couple of days? Yes. Are we at all likely to? NO. It’s possible to recover fingerprints from human skin…but historically it’s only been done a couple of times in actual case work. The key point here is that while this is possible, it is time consuming and unnecessary. Identifying someone from a blood sample requires DNA testing which takes Months. Waiting a couple of days to get a proper search warrant for blood, and a Known reference sample is the correct way to deal with this. Comparisons of 2 unknown samples are likely to be inadmissible in court anyway.
This story highlights two of the misconceptions of forensic science in the media. Fingerprints can be, and are recovered from any surface the suspect touches. The second misconception promoted by the media regards the speed of forensic analysis. We get this from detectives and attorneys too- not only can we test anything they can dream up, but we can have the results to them this afternoon. (Better known as the drive-through effect or McScience).
On Homicide they had a story in which the suspect was leaving notes behind sketched with chalk. So of course they took chalk samples and rushed them off to the lab. Within hours they had identified the chalk. I wondered a couple of things:
- Where did they get reference samples in that short a time?
- How did they get so lucky as to have a suspect using a rare artists chalk(which would be harder to find and reference see 1) rather than Crayola which can be obtained from every department store?
- Having used up their luck on 1 and 2, how did they get the suspect to use a credit card to pay for the chalk so they could rush a document examiner in on overtime to examine hundreds of receipts (from the one store that sold it locally- artists never mail order…) to locate the suspects signature? (Which he did in short order of course).
It should be noted that all the processing and testing in both these stories is possible and could be carried out on items of evidence. Band-aids or other items seized with the hope of using them as substitute reference samples are not evidence, and are not going to be tested except in rare circumstances. Chalk samples could in fact be compared, and the purchasers signature identified. The problem with this story line is that the process will take weeks or months to complete not a couple of days…
Unfortunately there isn’t much we can do about the presentation of our profession by the media. (Unless we can convince them to hire forensic consultants to review their scripts). Meanwhile we will simply have to continue to educate police, attorneys and jurors on a case by case basis.
Daryl W. Clemens, Editor