On January 12, 1998, Andrew Brannan was driving his truck at 98 miles an hour on a country road near his Dublin, Georgia, home when he was pulled over by Deputy Kyle Dinkheller. Brannan, a white-haired, 66-year-old man, got out of his truck, shouted profanities, and danced around, yelling, "Here I am, here I am ... [s]hoot me." He then attacked the deputy and a gunfight ensued, in which Brannan shot Dinkheller nine times with a rifle.

Video footage from the deputy's dashboard camera inflamed public opinion. Dinkheller was 22 years old and married, with one child and another baby on the way. Brannan received a death sentence and, on January 13, became the first person executed in 2015. But Joseph Loveland, an Atlanta-based attorney who tried to commute Brannan's sentence to life imprisonment without parole, says the jury and sentencing judge never heard the whole story.

"Every doctor who had examined Andrew confirmed that he was suffering for years before the crime from significant PTSD that was directly related to his service in Vietnam, and also suffered from bipolar disorder," Loveland said in an interview. "The two conditions interacted, leading to the crime he committed.”

Before he made headlines as a convicted murderer, Brannan was a decorated combat veteran struggling to hold his life together. He volunteered for service in the army in 1968 and trained as a parachutist. In 1970, he was deployed to Vietnam, where he served as a forward observer in an artillery unit. Brannan twice assumed command of his unit when the commanding officer was killed, and was awarded the Bronze Star and two Army Commendation medals for outstanding service. He was honorably discharged from active duty in 1971, and served in the reserves for several years.

After his discharge, Brannan tried to reintegrate to civilian life. But by the early 1980s, he began to experience severe psychological and emotional problems. He had a hard time keeping a job and his marriage fell apart. He sought treatment from the Veterans Administration (VA), which declared him partially disabled due to service-related post-traumatic stress disorder, or PTSD.

PTSD is a severe mental disorder that can affect intellectual and adaptive functioning, trigger flashbacks to traumatic events, and impair one's judgment. As its name implies, it can develop after exposure to a life-threatening event. Brannan’s case isn’t an isolated one: About 20 percent of military personnel who served in war zones in Iraq and Afghanistan and up to 30 percent of Vietnam War veterans have experienced it in their lifetimes, according to National Center for PTSD statistics.

Brannan was hospitalized several times and admitted into the VA's intensive PTSD treatment program. In 1991, the VA found he was 100 percent disabled due to service-connected PTSD. His VA psychiatrist, William Boyer, also diagnosed him with bipolar disorder in 1996. According to his doctors, Brannan withdrew from society, only had contact with other Vietnam War vets, and lived in a shack resembling a war-zone bunker.

"Andrew saw death repeatedly, including that of comrades and two immediate commanding officers, and remained plagued with guilt over these deaths decades later," Loveland wrote in the clemency petition to the Georgia Board of Pardons and Paroles. The court-appointed psychiatrist in his trial agreed that he suffered from both conditions. But although Brannan’s trial attorney argued that he was legally insane, which requires a high burden of proof to meet, Loveland says that key expert witnesses like Boyer did not testify at trial.

Despite the stigma attached to PTSD, the Department of Veterans Affairs emphasizes that most veterans suffering from the condition are not violent. In Brannan’s case, Boyer  testified before the court that the interaction of unmedicated PTSD and bipolar disorder contributed to his erratic and violent behavior at the time of the murder. Boyer explained  during a hearing that Brannan had been off his medication for days at the time of the shooting. In his medicated state, Brannan posed no threat of harming himself or others, the psychiatrist said.

“Rambo is not the face of PTSD,” Paula Schnurr, executive director of the VA's National Center for PTSD, said in an interview with The Desert Sun. “It's extremely important that we recognize that the majority of people with PTSD don't engage in criminal and violent actions.”

The risk of criminal behavior isn’t necessarily higher among combat veterans than with civilians, according to mental health experts. "I am unaware of data showing that people with PTSD are more violent than other people," Richard McNally, the director of clinical training in Harvard University's psychology department, told Reuters.

But some legal scholars and mental health experts suggest the criminal justice system should treat convicted veterans suffering from war trauma differently than other criminals. In a 2009 Fordham Law Review article, Anthony Giardino, an attorney and former Marine, argued that veterans suffering from service-related PTSD and traumatic brain injuries should receive a categorical exemption from the death penalty. "If the death penalty is truly only for the worst offenders, justice requires that combat veterans suffering at the time of their offenses from service-related PTSD or TBI [traumatic brain injuries] not be executed or sentenced to death," he wrote.

While PTSD cannot excuse criminal behavior, Giardino argues, it should reduce culpability. "PTSD can impair your ability to recognize that acting in a militaristic manner is not acceptable," he told me in an interview. "[Veterans with PTSD] might use their training in an inappropriate manner" while among civilians.

Giardino isn’t alone in making this argument. Mental-health experts Hal S. Wortzel and David B. Arciniegas made a similar case for exempting veterans affected by war trauma from the death penalty. Military training and combat, combined with traumatic experiences, may have an impact on aggression and behavioral control, the authors said in a 2010 article.

Although the Supreme Court ruled in 1986 that executing people with severe mental illness is unconstitutional, many death-row inmates who suffer from some form of mental illness, including schizophrenia, bipolar disorder and delusions, do not fall within that exemption. Under federal law, capital defendants are entitled to a psychiatric evaluation to determine their competency to be executed. However, there are no uniform sentencing standards for people with combat-related PTSD. The outcome in each of those cases depends largely on other circumstances.

"Presenting PTSD, TBI, and military training evidence ... during the sentencing phase of a capital trial represents one way to avoid subjecting combat veterans to the death penalty," Giardino, who served in Iraq, said in his article. The attorney said combat veterans with PTSD should receive a death-penalty exemption similar to those for minors and the mentally retarded.

Wortzel and Arciniegas noted that Giardino's proposed exemption may be too broad, since some combat veterans may have been "broken" before their military service. However, courts must engage in a balancing act to prevent "the injustice and immorality of executing a single combat veteran who has PTSD and/or TBI at the time of the crime," the doctors wrote.

"Some courts have considered war trauma in sentencing combat veterans," according to Giardino. "Many courts, however, would rather ignore this elephant in the room than confront the reality that the combined effect of government-sponsored military training and combat exposure transforms men and women into something quite different from their former selves," he wrote in the article.

Although PTSD has become a common defense in trials of combat veterans, the outcomes have been anything but uniform. An Oregon jury in 2009 found Iraq war veteran Jessie Bratcher guilty of murder but legally insane. Instead of serving 25 years in a maximum-security prison, Bratcher received treatment at the Oregon State Hospital. He was released last year after the state psychiatric review board found he no longer suffered from PTSD.

The Supreme Court overturned a veteran’s death sentence in 2009 because, among other factors, his lawyer had failed to disclose his client’s combat service as a mitigating factor during sentencing. "Our nation has a long tradition of according leniency to veterans in recognition of their service, especially for those who fought on the front lines as [defendant] Porter did," the court wrote in that opinion. "Moreover, the relevance of Porter’s extensive combat experience is not only that he served honorably under extreme hardship and gruesome conditions, but also that the jury might find mitigating the intense stress and mental and emotional toll that combat took on Porter."

Other veterans with PTSD like Brannan face the death penalty for similar crimes. John Darrell Thuesen, who killed his girlfriend and her brother in 2009, is currently on death row in Texas. Eddie Routh, a former Marine diagnosed with PTSD, may also be facing the death penalty in Texas in his upcoming trial for the murder of Navy SEAL sniper Chris Kyle. Routh's lawyer will reportedly pursue an insanity defense, but he questions whether his client can get a fair trial given the impact of box-office hit American Sniper.

Ultimately, Giardino says, the outcome of each case depends on the ability of defense counsel and on the laws of each state. "Different states have passed laws requiring courts to take into account PTSD and have defense counsel who understands those issues effectively present the background information, including military service and mental illness, accurately," he said.

Some states have also established specialized veterans courts in the last decade to recognize veterans with PTSD as a distinct category of offenders who need special treatment and help. The first veterans court was launched in 2008 in Buffalo, New York by Judge Robert Russell, who noticed similar symptoms among former military personnel who appeared in his courtroom. Some 98 percent of the veterans in the program have not had further run-ins with the law, according to court records. But those courts, which function much like drug courts, are limited to non-violent offenses.

Additionally, a veterans' group, the National Veterans Foundation, is creating a manual for lawyers on how to defend veterans with PTSD in court. The guidelines include finding witnesses from defendants' squads, who can testify about their combat trauma.

But PTSD defenses still cannot guarantee avoiding the death penalty in every case or in every state. "PTSD as an insanity defense in a murder case is hard to use because the person knows the difference between right and wrong," Landy Sparr, a forensic psychiatrist, told CNN. "They are not delusional or psychotic. For example, they do not believe they have killed a Martian instead of a human."

It's difficult for the legal system to truly grasp what veterans with PTSD have experienced. This lack of empathy is a key obstacle to change. Andrew Brannan and others like him may not gain sympathy from people who lost loved ones to senseless acts of violence. Until society realizes how combat can change service members, the fate of capital defendants with combat PTSD will remain an open question.