The revolver had been used in a felony, a robbery as I recall. It was submitted for fingerprints and I fumed it in the superglue cabinet. When I took it out for examination, I couldn’t believe my luck – the trigger was smooth, not ridged or grooved, and there was a beautiful, un-smudged print on the trigger. It was the core of a whorl pattern with plenty of points and even some clear Level 3 detail. It would be an easy ident.
I got a set of the suspect’s fingerprints and quickly excluded him. Somebody else had their finger on the trigger. Then a nasty, uneasy feeling came over me. I asked for the inked fingerprints of all the officers who had been involved in the case.
Sure enough, the print belonged to one of our patrol officers. I went to the detective assigned to the case and asked him what had happened. After he had asked a few questions of the officers, the story came out. They had wrapped up their field investigation and come back to the station to write reports. The revolved was laying out in the open on a table with some other evidence. It was unloaded and the cylinder was open. One of the officers picked it up, closed the cylinder, aimed it at the clock high on the wall, and dry-fired it through a couple of cycles of the cylinder. Another cop asked for it, and eventually every officer in the room had taken a turn dry firing the weapon at the clock.
Only when the Sergeant walked in did he remind his shift of Einsteins that the gun had been used in a felony and should be submitted for prints. Since it is rare to develop latents on firearms anyway, they decided to submit it without mentioning the dry fire episodes or including elimination prints of the officers. They figured no prints would be developed anyway and their negligence in handling the weapon would not be discovered.
In spite of all the training we in forensics try to do, we are plagued with contamination by thoughtless officers. DNA analysts live with it more than fingerprint examiners do. At one lab where I used to work, the DNA folks were always finding one officer’s DNA on every swab when he was involved in a case. It turned out that he was using his drinking water bottle to moisten the cotton swabs he used to collect DNA. Or a video on LinkedIn recently with an officer who had just put on his blue PVC gloves and was picking his nose. No risk of contamination there, right?
After the first few incidents in my career identifying the fingerprints of careless officers, I decided the best way to deal with them was to embarrass them, which would also set them up as examples for other officers to take notice of. Subsequently, as in this case of the officer’s fingerprint on the trigger, when I identified an officer’s fingerprints, especially on a crucial piece of evidence I would send a formal written memorandum of record to the supervisor to place in the officer’s file.
Education isn’t always a benign process in a classroom. Sometimes it happens in the field with consequences.