My innocent brother on death row

• Martina Davis-Correia
• guardian.co.uk 20 May 2009

Back in 1989 a police officer called Mark Allen MacPhail was shot dead during the early hours of 19 August in the car park of a Burger King in Savannah in my home state of Georgia. Along with several other people, my brother was in the car park at the time. The police decided Troy was the killer, he was arrested, charged and put on trial for his life.

So what was the evidence against my brother? It was actually entirely witness testimony based. There was no forensic evidence, no security camera footage and no murder weapon (which has never been recovered).

Good quality testimony from witnesses can of course contribute to a strong prosecution case, but my brother's conviction was the opposite. Yet, at Troy's trial in 1991 things did look really bad. Numerous people testified that Troy had pulled the trigger and all of Troy's protestations and good character references (which were exemplary) were to no avail. He got a death sentence.

But the case against him was actually just a prosecutorial facade and it's since fallen apart. Since 1991 no less than nine people who gave damning evidence (many in court) against Troy have recanted in sworn statements.

Why this big collapse? Because, as I've discovered since campaigning for my brother, the case against Troy mirrors a lot of capital investigations in the US. There's heavy reliance on "evidence" from dubious sources. In Troy's case the prosecution used testimony from a "jailhouse informant" (notoriously untrustworthy sources), a scared single mother convinced her parole would be revoked if she failed to testify against Troy, and an intimidated teenage Burger King employee called Antoine Williams who signed a police witness statement falsely claiming to see Troy shoot Officer MacPhail. Williams later admitted he hadn't seen anything and hadn't even read his signed statement because he was illiterate.

Another 15-year-old picked up by the police that night has since described his police interrogation like this: "Over the next couple of hours, three or so officers questioned me – at first, they called me a motherfucker and told me that I had shot the officer. They told me that I was going to the electric chair. They got in my face and yelled at me a lot – I just kept telling them that I didn't do anything, but they weren't hearing that. After four or five hours, they told me to sign some papers. I just wanted to get the hell out of there. I didn't read what they told me to sign and they didn't ask me to.

Actually this is just scratching the surface when it comes to explaining how the patched together case against my brother has fallen apart. Numerous people who never appeared at Troy's trial have since given affidavits all implicating another man, one known to carry a gun who was in the vicinity acting strangely at the time.

Two years ago Amnesty International published a 35-page report on it. Amnesty is now appealing to Georgia's state governor George "Sonny" Perdue to grant clemency in Troy's case.

I pray that Governor Perdue will act. The US capital punishment system is stubbornly resistant to re-examinations of death row cases even when, like in Troy's case, there's been an avalanche of changes since the original trial. Troy's stay of execution was lifted on Saturday and he's now back in real danger of being executed.

Meanwhile, our family and our fantastic supporters continue to fight. Amongst other things we've read the Guardian's series on British miscarriages of justice and we know it's never too late to right a wrong. And anyway, what else am I going to do?

As you'd expect, what happened in that parking lot in Savannah 20 years ago has come to dominate my life. It was a tragedy for Mark Allen MacPhail's family that a young man lost his life that way, but my brother has also had the best years of his life stolen from him. Back when I was a teenager I saw a pamphlet in a library about Amnesty's human rights work overseas. I'd always been a "good causes" kind of person and I became a supporter. This is one of the big ironies in my life. I thought I'd be helping prisoners of conscience in the Middle East or Africa, not campaigning for my own kid brother's human rights.

• This article was amended on 22 May 2009 to include the name "Sonny" which Governor Perdue is often known by.

For more information visit www.amnesty.org.uk/deathpenalty