From ABC News:
Those outdated techniques once commonly used by fire investigators, Lentini and others warn, may have landed dozens of innocent people in prison for fires they did not start. Dougherty's case is one of what is expected to be a string of legal challenges to arson cases from the 1970s, '80s and early '90s. [...]
"I'd have to say 10 [percent] to 20 percent of the cases decided in the 1980s and early 1990s were probably wrong, or could have been wrong," said John DeHaan, a former arson investigator with the California Department of Justice. [...]
In training exercises for veteran fire investigators conducted by the federal government, fewer than a quarter of investigators generally were able to identify the cause of test fires, said Steve Carman, who recently retired as a senior special agent at the Bureau of Alcohol, Tobacco, Firearms and Explosives.
Daniel Dougherty is on death row for the deaths of his 2 sons and another man, Cameron Todd Willingham, who was convicted based at least in part on similar techniques was executed in 2004.
This is one of the reasons I am suspicious of the death penalty.
I also know that unreliable forensic evidence isn't proof of a wrongful conviction. There was testimony that Dougherty confessed his guilt to multiple people and at least one of whom has since died.
Guilty people as well as the innocent loudly proclaim their innocence.