What’s the worst fabric a criminal can wear? Corduroy, says Connie Fletcher, who studied hundreds of crime scenes for Every Contact Leaves a Trace (St. Martin’s Press; $24.95), out in August. “Because of its thick naps, corduroy both sheds and picks up evidence,” she says. “Many cases have been solved from a single fiber.” A Loyola University journalism professor and Wilmette mother of two, Fletcher explains here how trace evidence can finger a killer at a crime scene (this one based loosely on a real murder in Michigan).



1. “The two most dangerous rooms in any home, crime scene experts say, are the bedroom and the kitchen,” notes Fletcher. “Why the kitchen? Weapons are everywhere. And people often do bills at the kitchen table. Two leading causes of domestic homicides in the U.S. are arguments over sex, which account for bedroom danger, and money.”

2. “A man calls 911, saying his wife has been shot. Detectives take the husband in for questioning, but he won’t talk. It is up to the forensic evidence to determine if the husband arrived after his wife was murdered, or if he himself is the killer.”

3. “This seems easy. Get prints from the gun; identify the offender. Two things are wrong with this approach. First, guns are often poor surfaces for prints to adhere to. Second, finding the husband’s prints on the gun only establishes that he has handled it in the past. However, in the act of firing the gun, the husband’s hand got pinched in the slide as he advanced the next round, leaving a microscopic bit of blood there-enough for positive DNA identification.”

4. “Directionality of blood can show who was present at a crime and where they were. The detectives bag the husband’s shoes as evidence. A drop of blood is found on the side of his right shoe. Only if the blood were on the bottom, could he say he stepped into it after finding the body.”

5. “The husband confesses. Says he shot his wife in self-defense after she charged him with a knife. There is a blade in the victim’s hand; however, it points toward her. This indicates staging, which is setting up a crime scene to look like something it isn’t-one unfortunate side effect of CSI and other crime shows. But the offender can make mistakes in the panic of the moment. Police doubt the husband’s story.”

6. “The blood spatter on the husband’s shoe, the knife pointed the wrong way, and the DNA captured from the gun helped detectives build the case that the husband murdered his wife and tried to stage it as self-defense. What sealed the case was that there was blood on the palm of her right hand where she had touched the gunshot wound. The normal reaction is to grab where it hurts. And she did. She had blood on her hand, but there was no blood on the knife. The knife was a staged afterthought.”

Illustrations: Colin Hayes