ON DECEMBER 8 , the state of Georgia carried out its fifth and final execution of the year, killing 47-year-old Brian Keith Terrell by lethal injection for a 1992 murder. It was a fight over money, the state said. Terrell forged checks belonging to an elderly family friend, then shot the man after he was found out. But for years Terrell and his lawyers insisted he was innocent — no physical evidence linked him to the crime, and, after three trials, the key witness against him recanted, telling a defense investigator that he had implicated Terrell in order to save himself.

In the end, however, this made no difference to the state of Georgia, nor to the U.S. Supreme Court, which denied Terrell’s final appeal around 11 p.m. on Tuesday. After a prolonged and painful search for a suitable vein — after an hour, the nurse finally stuck an IV into his hand, according to the Atlanta Journal-Constitution — Terrell died just before 1 a.m. He gave no last statement. But witnesses said he mouthed three words to a county sheriff in the front row: “Didn’t do it.”

Terrell was the 28th prisoner to be put to death in the United States since January, and the last of 2015. This made it a relatively slow year for executions. By contrast, 34 people died on the gurney in 2014 and 39 in 2013. The steady decline is part of a longer, well-documented trend: U.S. executions have fallen precipitously since peaking in the late ’90s, while new death sentences are down across the country and are handed out in a narrowing number of jurisdictions. Even in Texas, only three people were sentenced to death this year. Nationally, death row populations continued to shrink in 2015. As many experts have observed, in historical terms, the death penalty is dying.

Yet 2015 was still a wretched and messy year as far as the death penalty was concerned, one that did much to undermine our country’s vaunted claims to “evolving standards of decency.” Missouri executed a man missing one-fifth of his frontal lobe. Virginia killed a prisoner whose appeal for a stay of execution was still pending before the Supreme Court. Amid little public outcry, Texas executed a man named Lester Bower, who insisted he was innocent during his 30 years on death row — and whose case had quietly fallen apart.

States continued to cluelessly tinker with lethal injection, passing new secrecy laws to shield themselves from scrutiny — and relying on those laws to illegally obtain execution drugs from sketchy providers as far-flung as India. (As a backup for unavailable drugs, Utah went ahead and brought back the firing squad.) In Glossip v. Gross, the U.S. Supreme Court gave constitutional cover to the states’ lethal injection experiments, upholding the use of midazolam for executions, despite its short, ugly track record — and telling prisoners it’s their job to find a suitable alternative. (In Missouri, two men now find themselves arguing that they should die in the gas chamber instead of by lethal injection.) And in a particularly surreal display of incompetence and corruption, the state of Oklahoma, fresh off its Supreme Court win, came within moments of killing (the likely innocent) Richard Glossip using the wrong drug — and later revealed it had used the same drug to kill a man in January.

As a case study in death penalty dysfunction, 2015 would be as good a year as any.

THERE WAS SOME GOOD NEWS , of course. Moratoriums remained in place across the country. In Connecticut, which abolished the death penalty years back but kept 11 people on death row, a court ruled that those prisoners should be spared as well. In Nebraska, lawmakers made history by overriding a gubernatorial veto to abolish the death penalty — the first Republican-controlled legislature to do so in decades — prompting Gov. Pete Ricketts to desperately pour his own family money into a ballot initiative that would repeal the repeal.

There were rare instances of accountability for official misconduct: Texas prosecutor Charles Sebesta was disbarred for sending an innocent man to death row, while in California an entire DA’s office was removed from a major capital case after a defense attorney revealed vast and jaw-dropping misconduct in its use of jailhouse snitches.

Six death row prisoners were exonerated in 2015 — both a bright spot and a grim wake-up call — while others were officially pardoned and thus given a shot at compensation for their wrongful conviction. People facing execution were spared at the last minute — in Missouri, home to one of the country’s most active death chambers, Kimber Edwards had his sentence commuted by Gov. Jay Nixon just three days before he was set to die. And last month the Missouri Supreme Court threw out the conviction of Reggie Clemons, whose case became a rallying cry for Amnesty International. Both men faced execution despite grave doubts over their guilt.

As 2015 comes to a close, the number of death row exonerations now stands at 156, though many more people have been released without formally being cleared. Innocence continued to haunt the death penalty this year: “Serious unreliability” was one of the “three fundamental constitutional defects” cited by Supreme Court Justice Stephen Breyer in his remarkable, sweeping dissent in Glossip, which made the case for abolishing the death penalty completely.

Indeed, this year proved a bleak illustration of much of what Breyer argued in his 41-page dissent. One stark example: what Breyer describes as “unconscionably long delays that undermine the death penalty’s penological purpose.” Across the country, prisoners spend so many years on death row they are more likely to die of natural causes than be executed. It’s a slow torture (many on death row live in total isolation), not to mention a betrayal of the promise of “closure” offered to victims.

Among those who died before reaching the gurney in 2015 were Florida prisoners Jerry Wickham (after 27 years on death row) and Clarence Jones (after 26). Another Florida man, Gregory David Larkin, committed suicide on death row. He was the fourth prisoner to do so in the state since 2000. Prisoners died in Nebraska and Tennessee, and, in California, where the execution chamber has been dormant for almost 10 years, at least six death row prisoners died, the oldest at age 70. Most recently, on the night before Thanksgiving, 67-year-old Donnis Musgrove died on Alabama’s death row after fighting for almost 30 years to prove that he was innocent.

For others who lived to see the world outside in 2015, the death penalty demonstrated its cruel reach. After a futile fight for compensation, Louisiana exoneree Glenn Ford succumbed to lung cancer in June, just one year after his release from Angola Prison, where he spent 30 years on death row. In Indiana, a woman named Paula Cooper, who was once the youngest death row prisoner in the country, committed suicide after struggling to survive in a world that still generally saw her only for the crime she committed at 15.

SO WHAT ABOUT the 28 who were actually executed? There’s no denying they represented some brutal and vicious crimes. But they were also emblematic of the lie that we reserve death sentences for the “worst of the worst.” Among those killed in 2015 were prisoners with severe mental problems, people with strong innocence claims, and individuals who were clearly rehabilitated and deserving of clemency.

Take Georgia alone, the state that carried out the first and last executions of 2015. On January 13, Georgia killed 66-year-old Andrew Brannan, a decorated Vietnam veteran who survived extensive combat only to unravel upon returning home from war. He developed PTSD and was diagnosed as bipolar; by the time he shot a police deputy during a traffic stop in 1998, Brannan “was living a marginal, fearful life, living in a primitive homemade shack reminiscent of a bunker in Vietnam,” according to a doctor who examined him. The jury who sentenced Brannan never heard about his trauma or mental illness — persistent problems among those on death row, 10 percent of whom are veterans.

On the night Brannan was executed, The Intercept reported, law enforcement outside the Georgia Diagnostic and Classification Prison in Jackson expressed misgivings over the fact that Brannan had served in Vietnam. Other fellow veterans tried to save his life. “What does putting a man like Andrew Brannan to death say to my generation of veterans?” a man who served in Iraq and Afghanistan wrote to the Georgia Board of Pardons and Parole. “To me, it says that this country can exploit our youth to its gain and then, when it comes time … will discard you like yesterday’s forgotten garbage.”

Brannan was not alone in being executed despite his severe mental problems. Just two weeks later, Georgia killed Warren Hill, a man whose developmental history and low IQ had led him to be diagnosed as intellectually disabled by seven different doctors. In theory, such executions are forbidden. Atkins v. Virginia prohibited the execution of the “mentally retarded” in 2002, while in 2014, Hall v. Florida reined in states’ wildly disparate standards for deciding who qualifies. Georgia’s own standard of proof is the strictest and most absurd among the states: Georgia law dictates that prisoners like Hill must show intellectual disability “beyond a reasonable doubt,” a gross misapplication of a blunt legal concept for the purpose of diagnosing developmental disabilities.

Georgia also reiterated this year its willingness to execute in the face of lingering doubts. Marcus Ray Johnson was denied a new trial and executed in November despite questionable forensic evidence. But in some ways, the execution of a clearly guilty person — Kelly Gissendaner — was perhaps the most disturbing. When I asked one death row prisoner what he considered the low point of 2015, he pointed to her death.

Gissendaner was sent to death row for convincing a boyfriend to kill her husband in 1997. (The boyfriend was given a life sentence.) While on death row, Gissendaner came to embody the ideals of rehabilitation and redemption. She became a “model inmate,” a theologian, and a mentor and counselor to other women in prison. Her supporters ranged from prison officials to the Pope. When Gissendaner’s execution was halted in March due to concerns over “cloudy” execution drugs, it seemed briefly conceivable that Georgia might let her live. But a few months later, the state denied Gissendaner clemency for a second time. She died on the gurney on September 30, singing “Amazing Grace.”

Gissendaner’s death sent a grim message to prisoners across the country. It said that no matter how much you change behind bars, the state will reduce you to your worst mistake. For those facing execution, the death row prisoner told me, it robbed them of hope. “I’m sure it made a lot of men with worse cases feel like they don’t stand a chance with mercy alone.”

“To sum it up,” he said, “her case exemplified the lack of mercy in the American justice system at this time.”

Top photo: Crosses mark the graves of inmates in Huntsville, Texas, April 23, 1997. About 1,300 people from the Texas prison system are buried here, among them 200 who died on death row.