From http://www.nytimes.com/yr/mo/day/news/washpol/fbi-lab.html: The World Trade Center bomb was made of urea-nitrate, a compound that can be confused with non-explosive mixtures of the same ingredients. In an informal internal check of lab procedures, some senior FBI lab workers mixed human urine with fertilizer and added samples of that non-explosive mixture to the flow of material being tested by the chemistry unit. A manager in the chemistry lab identified the urine-fertilizer mixture as an explosive.

Just coincidentally, these errors imprison the innocent instead of freeing the guilty.

Still, Joseph E. DiGenova, a former U.S. attorney in Washington, said the issues raised in the report would allow defendants to contest lab findings against them and would permit people convicted of crimes to attempt to reopen their cases, based on the possibility of flawed forensic evidence.

"It's going to be a royal pain in the neck for federal judges and prosecutors and a godsend for defense attorneys looking for a means of getting their clients off," he said

Why not "proving their innocence"? A prosecutor - and one who does not respect our legal tradition of presumed innocence - is not a good choice for a quote here. Nowhere in the entire article is there evidence that the reporters talked to anyone outside the FBI/Justice Department milieu.

Scientists at the lab said they were often stifled in a lab run by non-technical field agents who had little knowledge of science and who regularly altered reports to help prosecutors. But law enforcement officials said there was little evidence that anyone had been wrongly convicted based on improper lab work.

Why isn't this the story? FBI agents regularly committed perjury, and we see a story about lab errors. Elliot Ness