Pucker Up For Ah…Lip Print Identification?

Good authors are look  for that little twist of strange for their novels and this might be a good place to start. Forensic scientists are always searching for new ways to link a suspect with a crime and one area of interest is in lip prints! I have to admit that only a small percentage of forensic scientists believe that lip prints can be individualized. Most of the support comes from practitioners in Europe but there are a few Americans as well and with more research who knows? Of course, the research to date has focused primarily on the physical properties of the impressions. The size and shape as well as the characteristics of the creases. Creases have been shown to be unique in other areas of the body like palms, fingerprints, and footprints so there is some support for using these features. Obviously one important factor is the clarity of the reproduction of said features. Are they smeared on with a heavy coat of lipstick or a true latent impression. If the clarity of the impression is poor then even advocates of lip print identification are limited in what associations they can declare.

No matter what camp you’re in however, there is additional value to be found in lip prints. I can think of two cases in my career where lip prints were found. So not real common, but valuable nonetheless. One reason we don’t find too many is that suspects don’t usually leave them. When we find them though the lip prints can reveal some important clues. The location of the print can be revealing. Imagine a set of lips on a dead person’s forehead? What does that say to you? How about on the body of a rape victim? Probably a different message right?  What if they are found on a letter from a stalker or jealous spouse? Maybe they are on the shirt collar of a deceased husband. No mater where they are found the location can be very telling to a CSI and suggest motive or suspects that need to be contacted.

One question I get from time to time is whether you can tell the gender of the lip smoocher. The short answer is no. We’d like to assume that lip prints (especially with lipstick) are female but men can certainly leave such prints as well and may even do so to stage a crime scene. Aside from the analysis of the physical properties of the lip prints there are some other key pieces of evidence that may help link the kissing criminal. The first obvious one is DNA. When a person leaves a latent or patent impression their DNA is a part of that impression. Technology has progressed to such a degree that analysts can get DNA profiles from extremely small samples. That is almost as good as a fingerprint.  If the impression is in lipstick, gloss, or other material then analysts may be able to classify that cosmetic. This link wouldn’t be unique as many people might own that particular make and color but it helps. Coupled with a DNA profile and physical features it may help to link or exclude a person from leaving the prints.

So if you’re looking for an unusual type of evidence to include in your crime novel consider using lip prints. You can see from the examples above that lip prints may convey anything from compassion to infidelity. They may even be accidental (pressing a face up to a window to look inside).  For me, I am not convinced they can be individualized but I haven’t done enough research to know for sure. Regardless, lip prints are cool and they can reveal a number of things to your characters and readers. Consider how you might use lip prints to convey a message or motive in your next scene!