Matthew Buendia is about to go on trial for attempted murder after shooting a deputy two years ago.
But long before the shooting, the former Marine was diagnosed with Post-traumatic stress disorder.
Doctors say it was from his time in Iraq and Afghanistan.
"Buendia saw combat, saw other people die in front of him," O'Brien said.
Then came the encounter that got him in trouble. In September of 2011, Deputy Lyonelle De Veaux showed up to Buendia's apartment to investigate claims he was beating his girlfriend.
Buendia fired nine shots at her, hitting her three times.
And she remembers what Buendia was worried about moments before the shooting.
"He asked me about a dog," De Veaux said.
O'Brien says Buendia had a dog Afghanistan that became his constant companion.
"His unit took in a dog that unfortunately had to be put down, and Matthew was the one who killed it," O'Brien said. "His unbelievable concern about a dog prior to him firing a weapon, it shows you he had no idea what he was doing."
O'Brien says what it all adds up to is this: Buendia is not a cold-blooded cop-killer.
"If Matthew Buendia did not suffer from PTSD and simply shot a police officer like Dontae Morris, then I completely understand saying he needs to take responsibility for it," O'Brien said.
Dr. Jeremy Gaies is a licensed psychologist who says when it comes to PTSD, anything can trigger a flashback.
"The re-experience of the actual event is one of the hallmarks of Post-traumatic stress disorder, so it could be a re-experience of being in a combat situation," Gaies said.
O'Brien argues Buendia is not a cop killer, but a wounded man with the mental scars of war.
But to keep his client out of prison, he will have to convince a jury.
FOX 13 / WTVT-TV
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