You’ve found several prints at the murder scene and you ran them through AFIS. This time luck was on your side. You got a hit on two of the latents. The first belonged to one of the usuals, a guy who goes by the street name “Popcorn.” You’ve arrested Popcorn several times over the years for assault, a few larceny charges, and a B&E or two. The dead guy was one of Popcorn’s card-playing buddies. Popcorn definitely could be good for this one.
The second suspect is an older man, Ima Forger, with a record of writing bad checks and one charge of embezzlement that occurred almost ten years ago. Violence just doesn’t fit. But, his prints were found at the scene. So, you round up both men and haul them back to your office for a little I&I (Interview and Interrogation).
Both men admit to visiting the home of the deceased, a Mr. I.M. Coldnclammy. Forger admits to being there, stating that the two of them had shared a pizza and watched the Red Sox and Yankees game. He claimed that his friend was very much alive when he left. But Forger also stated that just as he was leaving, Popcorn showed up and boy did he ever look mad. Forger said he could hear the two men arguing all the way from the bus stop in front of Coldnclammy’s house, some fifty-feet away from the front door.
Popcorn, however, says he hadn’t been to Coldnclammy’s house in over two weeks. But he has no solid alibi and everyone who knew Coldnclammy has already told you that he and Popcorn were not on good terms—something about one owing the other a great deal of money. And, there’s a rumor floating around the streets that Coldnclammy has been seen around town with Popcorn’s girlfriend on his arm.
So, all you have so far is the word of two crooks and a couple of fingerprints. One thug says he was there and the other says he wasn’t. But one man clearly implicates the other. You glance to the fingerprints. Both look the same to the naked eye.
They’re both attached to a white backing covered by the clear plastic of the hinged lifter from Sirchie Fingerprint Laboratories, you’re favorite brand.
What if the prints could tell you which man was truthful? The only way that could happen is if you knew the age of the prints. If Popcorn’s print was older than Forger’s, well…
Actually, it is possible to tell the age of a fingerprint, and it’s done by using a sensor that detects extremely faint electrostatic charges, such as those occurring over the surface of a fingerprint. Not only does this method allow the technician to successfully photograph the formerly invisible fingerprint, the process also detects the gradual reduction of electrical charge as the print ages. And, when compared to the time a crime occurred, officials can now eliminate or include potential suspects as the possible perpetrator of the crime in question.
In the case of Popcorn and Forger, well, the print was hotly charged and wasn’t very old. Definitely not two weeks old. So, you’re able to rule out Popcorn as a suspect for this crime. But he’ll be back. Forger, on the other hand, confessed when confronted with the “electrifying” evidence against him