Amnesty International UK Communications Director Mark Lattimer said:

'The execution of Alex Williams would be further evidence that the USA is a rogue state when it comes to the death penalty .

'It leads a tiny handful of countries flouting the global ban on the use of the death penalty against Children's rights - those under 18 years old at the time of the crime.'

Alex Williams was 17 at the time of the murder of 16-year-old Aleta Bunch in 1986. If executed, he would become the fifth child offender executed in the USA this year, more than in any year since 1954. It would also mean that the US has executed more child offenders in just over seven months than the rest of the world has in the past seven years.

'There is almost no other country on the planet where Alex Williams would be put to death,' Mr Lattimer said. 'In the past three years, only Iran and the Democratic Republic of Congo are known to have executed child offenders.'

Contrary to international standards, Alex Williams, like many US capital crime defendants, was denied his right to adequate legal representation. Williams' lawyer effectively abandoned him at the 1986 trial by not investigating the teenager's history of appalling childhood abuse and evidence of mental illness to present in mitigation.

Alex Williams' mental illness has worsened on death row, and the state has on occasion forcibly medicated him to control his symptoms, which include delusions and auditory and visual hallucinations. He has been variously diagnosed as suffering from paranoid schizophrenia and schizoaffective disorder with bipolar features.

The report puts Alex Williams' case into a context of increasing national and international concern surrounding the US death penalty. Calls for a moratorium have increased since the Governor of Illinois halted executions in his state because of its 'shameful' record of wrongful convictions* in capital cases.

Amnesty International members worldwide are appealing for clemency for Alex Williams. The Georgia Board of Pardons and Paroles is due to meet to consider clemency on Tuesday 22 August.

* A Georgia case is one that is now central to the debate over the risk of executing the wrongfully convicted. In July 2000 a judge authorised DNA testing of evidence from the case of Ellis Wayne Felker, executed in Georgia on 16 November 1996 despite doubts over his guilt. It is believed to be the first time a US judge has issued such an authorisation. CBS News and three newspapers are funding the DNA testing.