A Metro police officer abruptly resigned after police say he falsified records to cover up a faulty ballistics report.more>>
It can mean the difference between solving a crime and putting the wrong person behind bars.
Earlier this year, Metro police shut down part of its crime lab because of faulty work.
Since that time, the Tennessee Bureau of Investigation has reviewed more than a dozen cases involving the ballistics lab.
The TBI has found some problems. The agency points to at least three cases where agents disagree with Metro's findings.
Metro said the differences are small, but not everyone agrees.
Police said he falsified records to cover up an obvious error. Michael Pyburn abruptly resigned in April after more than 10 years in the Metro ballistics lab.
Police shut down the lab and reassigned the other two officers for being unqualified.
The TBI has been reviewing the lab's work ever since.
"We are taught as a society to trust the police department," said attorney Ed Gross.
He represents James Pollard who is charged with first degree murder. Gross was surprised to learn from NewsChannel 5 Investigates that Pollard's case is one in which the ballistics report is now being questioned.
"I would have liked to have known the second it came out because we are talking again a first-degree murder case," Gross said.
Prosecutors said Pollard went to a North Nashville apartment two years ago and murdered Jamil Branhan.
Metro's ballistics lab determined two bullet fragments found inside the victim came from the same gun.
But the TBI could not conclude they came from the same gun and agents will not testify to that under oath.
"When there is a disagreement between experts this is serious and that is the reason I believe it is so serious," Gross said.
Gross said it's unlikely the difference will clear his client, but it may bolster his self defense claim.
"Anytime you have a discrepancy, when you are doing a criminal case obviously those raise red flags because you are dealing with someone's life," said attorney Deon Owensby.
He represents another client in the Branhan murder case.
"I was surprised actually very surprised those discrepancies were there," he said.
The district attorney's office asked the TBI to review 28 Metro cases set for trial. Of the 14 completed so far, the TBI has found problems with two.
NewsChannel 5 Investigates has learned there was a problem with a third case.
The Metro ballistics lab said firearms evidence linked DeQuan Crowell to an unsolved crime. The TBI disagreed.
"We don't see anything that is a systematic problem that is occurring in every case of something like that," said District Attorney General Torry Johnson.
He said he worried the review would uncover larger problems. But he said have been minor differences.
When asked if he was surprised that there would be the minor discrepancy, Johnson said, "It's hard to compare. I don't really know what the best answer is for that."
But defense attorneys said it is surprising given the weight juries give to ballistics evidence. It's scientific and, they said, there should not be differences between agencies.
"Do you think anyone is in jail now who may be there wrongly?" asked NewsChannel investigative reporter Ben Hall.
"From what I'm looking at right now, of course I can't say positively no, but it doesn't appear that that is the situation," Johnson said.
So far, the TBI has not reviewed any past convictions. It is only reviewing cases with upcoming trials.
Prosecutors said if an attorney has a problem with a past conviction he should bring it to their attention.
Metro police are working to rebuild the crime lab. The department hopes to hire a quality assurance director by September.
In the meantime, the TBI continues to do all ballistics testing for the police department.