Harant's testimony differed in Washington's hearing last month. He said that in "very rare" instances - he said less than 5 percent of the time - he will conclude that a particle is gunshot residue if it contains only barium and antimony, and if he can rule out other possible sources for the particle.
Themelis called it "disturbing" that Harant's testimony before him differed from his testimony in April. Harant explained the difference by saying that the April case involved a three-element particle, and he didn't see the need to discuss in detail the instances in which he thinks a two-element particle can be called gunshot residue.
Themelis said Harant's conclusion was out of step with the scientific community and excluded the gunshot residue evidence from the Washington case. (Washington later pleaded guilty to two charges of weapons violations and was sentenced to time served.)
All FBI crime labs and 200 evidence labs operated by RJ Lee Group, which does forensic analysis for the Anne Arundel and Baltimore County police departments, have the more stringent standard of three elements.
The current computer software that Harant's lab uses to analyze suspected gunshot residue classifies only the three-element particles to be uniquely gunshot residue, a change from older software that also considered barium-antimony particles to be unique.
Jablow, the police spokesman, said that the American Society for Testing and Materials still considers some two-element particles to be gunshot residue and that city police protocol also allows for that finding. Maryland State Police also use that standard, he said. "We're very comfortable that we're right on this issue," Jablow said.