The Surprisingly Simple Clues Left Behind At Crime Scenes

We kicked in the seedy bungalow's back door, armed with a search warrant.

"Smell that?" Sergeant Jill Prunty, my partner on the Integrated Homicide Investigation Team, stopped short.

"Yeah." I caught it, too.

"Smells like" -- Jill whiffed the air like a bear -- "the morgue."

"It's Iso." I recognized it immediately. "Isopropanol. Somebody tried to clean up."

It's not uncommon for criminals to try covering their dirty deeds, but you'd be surprised at the telltale details they commonly overlook in their haste to leave the scene of the crime.

Jill and I were following information that a biker named "Zeke" had been whacked, and then taken out and dumped. No body yet, but Zeke was missing. Our source was solid. Someone murdered Zeke in this house.

"Look at that." Jill pointed to three iodine-colored spots on the tile floor. She squatted. "What's this stuff?"

I slid on my glasses and got within inches. Bloodstains. Tiny -- but then all trace evidence is miniscule. And it's usually trace evidence that becomes a big deal at trial.

"Far as we go, Jill." I thumbed toward the door. "Till forensics get here."

I wouldn't say this was a typical crime scene. Criminals rarely go as far as using isopropyl alcohol (a common disinfectant), but they often try to erase what they think is glaring evidence. Trouble is, they don't know what homicide detectives and forensic crime scene examiners do, and that's what to look for in evidence.

Every experienced murder cop and forensic tech follows Locard's Exchange Principle. Who, you ask? Edmond Locard was the 19th-century pioneer of modern forensics -- the real Sherlock Holmes -- who held the belief that the perpetrator of a crime will bring something into the scene, will leave with something from it, and that both can be used as forensic evidence. Criminologist Paul L. Kirk summed up Locard's theory as:

Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these, and more, bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value.

Locard was dead right. Every contact leaves a trace. Minute particles easily cross-transfer from one surface or substrate to another and remain as mute witnesses long after the bad guys vanish from the scene.

In my career as a homicide detective, and later as a forensic coroner, I've not only seen the usual evidentiary suspects like blood, semen, saliva, mucous and hair, but also some creative exhibits such as food waste, lipstick smears, glove prints, printer ink, potting soil, cut wires, grease, cigarette butts, tea stains, insects, pollen and, most interesting of all, a perfect dental impression in a wad of chewing gum.

The Forensic Identification Officers -- the CSI guys -- arrived at the bungalow in minutes. First they photographed Zeke's entire murder scene. Then Jill and I dressed in our bunny suits (white Tyvek coveralls that are more for show than go) and began our search. First for the obvious, and then for the not so obvious.

Jill's gaze strayed to a swirl of mop marks on the kitchen floor. "Check this out." She nodded toward the sink. There was no need for Luminol or a Luma-Lite to find this blood smear.

"You don't suppose?" Jill peeked under the sink. The garbage can sat empty with its plastic liner gone. Forensics lifted a beautiful set of prints from the side.

"Could they be this dumb?" Jill had moved to the broom closet. The mop was still in the bucket, which reeked of Iso. More powder on the handle and more useable prints. It was pretty evident that Zeke had been shot in the kitchen, just as our source informed us.

But what about motive? Our suspicion was drugs. We brought in one of the most sophisticated crime-scene weapons -- a toothy German shepherd named Trooper, who sniffed his way to a desk in a back room. Underneath was a pane of glass showing white residue.

Meanwhile, we ran the prints through AFIS and got a hit. Officers scooped up the suspect, who quickly ratted out his accomplice.

In all, Sergeant Jill Prunty entered 29 pieces of incriminating evidence at that trial: 18 found at the crime scene and 11 found on the culprits, including high-grade China White heroin with a chemical signature as unique as the DNA from Zeke's blood found on their clothes.

That crime scene was anything but spotless.

For a look at how two brothers with a crime-scene cleaning business get wrapped up cleaning up for the mob, watch "Spotless," premiering November 14 10|9c only on Esquire Network.