Investigators exit the apartment of Condit after concluding their search
Lawrence Kobilinsky is the Associate Provost of the John Jay College of Criminal Justice in New York City and a forensics expert. He explained the nitty-gritty of the investigative techniques that police are using in the Condit case.
TIME.com: Gary Condit agreed this week to take a lie detector test about his involvement in Chandra Levy's disappearance. How can any information coming out of that test be used?
Lawrence Kobilinsky: The low down on polygraphy is the following. It's not permissible in court. In a hearing in 1923 it was found to be unreliable, and although technology has improved and polygraphy is quite effective, it is still considered unreliable. There are reports of false positives rather than false negatives, which could make an innocent person look guilty. The fact of the matter is that all law enforcement uses polygraphs. In my opinion, if it is performed by a person who is highly trained and expert, it is very informative tool. But though it should be used for investigative purposes, it should not be used in the courtroom. It is a good, useful technology but it's not perfect.
How does the polygraph test work?
The instrument measures different kinds of physiological parameters, for example, perspiration and respiration, your rate of breathing. One of the big problems here is that it's possible to get what looks like a lie that's really the physiology of the person, responding to the situation.
How can someone fool the test?
There are people that can control their physiological functions — perhaps by thinking of other things while being questioned, so you wouldn't necessarily increase your respiration. The point is that it would be useful for Condit to use this to clear himself, but I can certainly understand why, if somebody is innocent, they'd be reluctant to put themselves in a situation where there might be a false positive.
What about the police search of Condit's DC apartment Tuesday night? It's been ten weeks since Levy disappeared — what could police hope to find in his apartment?
When you go into this apartment and you're very suspicious that something could have happened months earlier, you don't know the history or what went on in the apartment. If there was any biological evidence it could have been cleaned up.
It's been established that she's been in the apartment, so finding her hair wouldn't be a surprise. But if you find multiple hairs with roots attached, that could indicate that it was pulled out forcefully. Or there could be microscopic blood spatter — these are things that are invisible to the naked eye but can be seen with (available technology), and that would be very suspicious.
How do they show the blood stains?
We're talking about a very intense light force that can vary in its wavelength. So you can chemically excite the chemicals or molecules within fingerprints or blood, and that excitement makes the specimen glow — it becomes visible to the naked eye. Then you'd have to remove whatever you're looking at and bring it back to the lab.
Spatter might indicate that it was created by a forceful traumatic event. The spatter pattern can reveal a lot about what created it. But the bottom line is they're going in to a scene that hasn't even been established as a crime scene. They have to collect evidence so that later, if they need to, they can go back and make sense of it.
So they are collecting anything they can as a precautionary measure?
Remember Jon Benet Ramsey — at first the police treated it as a kidnapping and didn't take proper steps at the home, preserving evidence? I think you have to get in there — keep an open mind and get in as soon as possible so evidence isn't lost.
Since he had a relationship with her it makes perfect sense to do what they're doing. There still may be evidence present if something happened in the apartment. But remember, she's been there — if you find something of hers, so what! It doesn't mean anything. If there's a hair, maybe they just didn't vacuum well. It really depends on whether her biological specimen is there and they're able to glean some information from a thorough analysis.
God forbid if she's dead and they find evidence on her body that creates an association with Condit, then he's got to explain that. Even that is not absolute proof, but it's suspicious. Part of forensic science is interpreting the evidence, and you can interpret in different ways. Not only do you have to reconstruct the events leading up to the crime, but after you do the analysis you've got to interpret it.
Is Condit being treated as a murder suspect, though there is no murder investigation at this point, and the police insist that he isn't a suspect?
I think there's no question that Condit is a suspect. They don't want to say that he's a suspect because at this point there's no crime. She may have committed suicide, she may have been abducted, she may have left the country. She may not want to be found, though I think that's extremely unlikely. Someone can be convicted of murder without a body, but there's no evidence of a crime yet. They have to be careful calling him a suspect. He's the center of attention, basically.
When an innocent person is caught up in the criminal justice system it's very hard to exonerate yourself. You have to keep you fingers crossed that the system is good enough to prove innocence.