By Jeff Jeffrey
Updated 4:40 p.m.
The defense in the Robert Wone trial opened its case this morning in D.C. Superior Court with Nicholas Petraco, an independent forensic consultant from New York who specializes in hair and fiber evidence.
Under direct examination by David Schertler of Washington's Schertler & Onorato, Petraco testified that the t-shirt worn by Wone at the time of his death could not be excluded as the source of fibers on the knife found near his body. Wone was stabbed multiple times in the chest.
The source of the fibers is a matter of dispute between the prosecution and the defense. A D.C. police department expert had written that the fibers found on the knife were “slightly dissimilar” from the t-shirt fibers and that “because of these differences, the white cotton fibers recovered from the knife blade could not be associated to the shirt.”
Petraco testified that, when he analyzed fibers taken from the t-shirt and from a towel found at the crime scene, which has also been posited as a source of the fibers on the knife, there were no physically distinguishable differences between the fibers of the two white cotton fabrics.
The court broke for lunch at about 12:30 p.m. and will reconvene at 2 p.m., at which point the prosecution may cross-examine Petraco.
During cross-examination of Petraco this afternoon, Assistant U.S. Attorney Rachel Lieber asked him whether he could rule out the towel either as the source of the fibers on the knife. He said, “I cannot.”
There was an also an brief exchange between Lieber and Petraco over one of the organizations listed on his curriculum vitae.
During his testimony this morning in which he established himself as an expert, Petraco said that he had been a member of the Scientific Working Group on Materials Analysis, which according to its website offers guidelines and best practices for forensic experts dealing with fibers, glass, paint, and tape.
Lieber asked whether Petraco was still a member of the group. He replied that he was not anymore because he was asked to leave. When she asked why, Petraco said he did not know.