We're getting close to being able to prove such a thing. One case currently is perculating in Virginia, one in Oklahoma, one or two in Texas.
And now, suddenly, this story pops up in today's Chicago Tribune:
Texas man executed on disproved forensics
Fire that killed his 3 children could have been accidental
By Steve Mills and Maurice Possley
Tribune staff reporters
Published December 9, 2004
CORSICANA, Texas -- Strapped to a gurney in Texas' death chamber
earlier this year, just moments from his execution for setting a fire
that killed his three daughters, Cameron Todd Willingham declared his
innocence one last time.
"I am an innocent man, convicted of a crime I did not commit,"
Willingham said angrily. "I have been persecuted for 12 years for
something I did not do."
While Texas authorities dismissed his protests, a Tribune
investigation of his case shows that Willingham was prosecuted and
convicted based primarily on arson theories that have since been
repudiated by scientific advances. According to four fire experts
consulted by the Tribune, the original investigation was flawed and it
is even possible the fire was accidental.
Before Willingham died by lethal injection on Feb. 17, Texas judges
and Gov. Rick Perry turned aside a report from a prominent fire
scientist questioning the conviction.
The author of the report, Gerald Hurst, reviewed additional
documents, trial testimony and an hourlong videotape of the aftermath
of the fire scene at the Tribune's request last month. Three other
fire investigators--private consultants John Lentini and John DeHaan
and Louisiana fire chief Kendall Ryland--also examined the materials
for the newspaper.
"There's nothing to suggest to any reasonable arson investigator that
this was an arson fire," said Hurst, a Cambridge University-educated
chemist who has investigated scores of fires in his career. "It was
just a fire."
Ryland, chief of the Effie Fire Department and a former fire
instructor at Louisiana State University, said that, in his workshop,
he tried to re-create the conditions the original fire investigators
When he could not, he said, it "made me sick to think this guy was
executed based on this investigation. ... They executed this guy and
they've just got no idea--at least not scientifically--if he set the
fire, or if the fire was even intentionally set."
To read the whole story (it's long!) go here.