Trace evidence expert says work like a 'jigsaw' puzzle
Alexander Oliva
Issue date: 3/28/06 Section: Campus
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03/28/06 - With all the different pieces of evidence used when investigating crime -- eyewitnesses, video surveillance, blood -- the best evidence is often fitting the broken pieces back together.
Virginia Maxwell, who works with the Connecticut State Crime Laboratory, spoke on Friday as part of the ongoing University of Rhode Island Forensic Science Seminar Series. Her talk focused on her expertise, trace evidence.
The problem with a lot of physical evidence, she said, is that there isn't 100-percent surety most of the time. However, when you get two pieces of broken glass or a knife blade, or paint chips, investigators can fit the two pieces back together.
"We're putting the two pieces back together like a jigsaw," Maxwell said. No two objects, she said, will snap in the exact same way. Because of this, it gives investigators completely reliable evidence.
There are some drawbacks to this technique, though. For one, "Trace evidence is very time-consuming," Maxwell said. With potentially thousands of tiny pieces of debris in and around a crime, picking out the relevant ones can be a huge chore.
However, since trace evidence can also be quicker and more versatile than DNA testing, it is often used to provide enough evidence for authorities to obtain warrants.
Trace evidence is not considered as trustworthy as DNA evidence, however.
"Juries want DNA, and prosecutors want DNA," Maxwell said.
And although in most cases trace evidence is very useful, there are cases where it is impossible to use. For example, Maxwell said, "If you have a domestic situation, any evidence can be explained away by two people living in the same house."
Despite these limitations, trace evidence can show definite links between two people or objects. If investigators find the paint from two cars on each other, they can tell the two vehicles came into contact without a doubt.
One case Maxwell mentioned involved a hit-and-run on Route 2. There were no witnesses, and no apparent leads. The only thing investigators had to go on were some paint chips found in the exhaust pipe. At a glance, one of the investigators well versed in car paint could tell the paint was used exclusively on Pontiacs from the mid-1980s, based on the color flakes in the paint.
Later, investigators also found a small piece of a license plate, with only the edges of one number and one letter showing. Based on this evidence, investigators were able to narrow their search down to a single car in Connecticut, which was quickly located.
There are other, more rare uses of trace evidence, such as soil analysis, or determining whether or not headlights were on at the time of a crash.
Virginia Maxwell, who works with the Connecticut State Crime Laboratory, spoke on Friday as part of the ongoing University of Rhode Island Forensic Science Seminar Series. Her talk focused on her expertise, trace evidence.
The problem with a lot of physical evidence, she said, is that there isn't 100-percent surety most of the time. However, when you get two pieces of broken glass or a knife blade, or paint chips, investigators can fit the two pieces back together.
"We're putting the two pieces back together like a jigsaw," Maxwell said. No two objects, she said, will snap in the exact same way. Because of this, it gives investigators completely reliable evidence.
There are some drawbacks to this technique, though. For one, "Trace evidence is very time-consuming," Maxwell said. With potentially thousands of tiny pieces of debris in and around a crime, picking out the relevant ones can be a huge chore.
However, since trace evidence can also be quicker and more versatile than DNA testing, it is often used to provide enough evidence for authorities to obtain warrants.
Trace evidence is not considered as trustworthy as DNA evidence, however.
"Juries want DNA, and prosecutors want DNA," Maxwell said.
And although in most cases trace evidence is very useful, there are cases where it is impossible to use. For example, Maxwell said, "If you have a domestic situation, any evidence can be explained away by two people living in the same house."
Despite these limitations, trace evidence can show definite links between two people or objects. If investigators find the paint from two cars on each other, they can tell the two vehicles came into contact without a doubt.
One case Maxwell mentioned involved a hit-and-run on Route 2. There were no witnesses, and no apparent leads. The only thing investigators had to go on were some paint chips found in the exhaust pipe. At a glance, one of the investigators well versed in car paint could tell the paint was used exclusively on Pontiacs from the mid-1980s, based on the color flakes in the paint.
Later, investigators also found a small piece of a license plate, with only the edges of one number and one letter showing. Based on this evidence, investigators were able to narrow their search down to a single car in Connecticut, which was quickly located.
There are other, more rare uses of trace evidence, such as soil analysis, or determining whether or not headlights were on at the time of a crash.
