Spring Break
Mertz's DNA a likely match
Shauna Gustafson
Issue date: 2/11/03 Section: Local & State
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DNA evidence showed Anthony B. Mertz as a likely match to a DNA profile found under the fingernails of Shannon McNamara.
While Mertz's profile was not guaranteed as the only match, expert witness Jennifer Lu, a scientist at the Illinois State Police forensics lab in Springfield, said there was a 1 in 1.8 billion chance among white individuals to match the profile.
Keith Laski and Brian Beavers both were able to be excluded from matching the profile, Lu testified.
Mertz is charged with first degree murder, aggravated criminal sexual assault and home invasion in the June 12, 2001, murder of McNamara.
A mix of two DNA profiles found under McNamara's fingernails, specifically on the right hand, showed one as a match to McNamara's DNA, the other as a profile from which Mertz could not be excluded as a match. Lu said 1 in 29 billion black individuals would match the profile, 1 in 1.8 billion white individuals and 1 in 1.1 billion Hispanic individuals.
Lu identified the world population as being between 6 billion to 7 billion. State's Attorney Steve Ferguson had 2000 U.S. Census information into evidence, showing in 2000 that 281,421,906 people lived in the United States, with 211,460,626 of them being white.
No two people in the world have identical DNA, unless they are identical siblings, Lu said.
During cross examination, defense attorney Paula Phillips asked Lu if DNA evidence is absolute and if it was an exact science. Lu said it is an exact science and is absolute at least in the sense of excluding those who are not a match.
Phillips focused many questions on the procedures used by the lab to ensure no contamination occurs and to clarify if other potential matches could have been made.
No other person matched from the standards Lu received from Mertz, McNamara, Laski and Beavers.
Lu testified her findings were reviewed by two other people in the lab, including her supervisor, for correctness.
In tests of bloodstains from McNamara's apartment, Mertz's, Laski's and Beavers' DNA was able to be excluded from a piece of latex glove, a piece of wall, the handle of a box cutter and the blade of a knife that was found in a dumpster near Mertz apartment. McNamara's DNA was evident on each of these items.
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