By Matthew Davis
BBC News, Washington
The life of a convicted murderer is hanging in the balance while a US jury considers whether his intelligence has increased enough to allow him to be put to death.
Atkins faces a lethal injection if he is ruled mentally fit to be executed
Daryl Atkins was named in a landmark Supreme Court ruling in 2002 that said it was unconstitutional to execute the mentally retarded.
But the intellectual stimulation the killer got by constant contact with lawyers in the case is thought to have raised his IQ above the threshold of 70, which puts him in line for the death penalty in Virginia.
The 27-year-old's case has divided lawyers and psychologists and has become the latest battleground for those arguing for and against state-sanctioned executions in America.
It raises questions over who should decide on a criminal's competency and whether knowing details of their crime can skew that life-or-death decision.
Atkins is a violent killer, with a string of felony convictions.
In 1996, he and another man abducted Eric Nesbitt, 21, a US airman from Langley Air Force Base.
They forced him to withdraw money from a cash machine, then took him to an isolated field where Atkins shot him eight times, killing him.
Atkins' IQ was tested in 1998, and was found to be 59, well below the level at which a person is deemed retarded in Virginia.
But when he was retested following the Supreme Court ruling defence experts found his IQ had risen to 74, while prosecutors said it was two points higher.
Dr Evan Nelson, who tested Atkins in 1998 and 2004, wrote in a report last year that "his constant contact with the many lawyers that worked on his case" gave him more intellectual stimulation in jail than he got during childhood.
"That included practising his reading and writing skills, learning about abstract legal concepts and communicating with professionals."
But prosecutors say Atkins was never retarded in the first place, indicated by the fact that he was able to load a gun, direct the victim to a cash machine and identify a remote spot for the killing.
Faking a result
For a person to be legally defined as mentally retarded in the US, the retardation must have been present before the age of 18.
The case is the latest battleground for those for and against the death penalty
It is expected that the jury will be asked to consider a wide range of evidence to determine Atkins's mental capacity.
This will include records from his childhood, various intelligence and memory tests and interviews with people who have known him as an adult.
An independent forensic psychologist, Dr Bob Stinson, told the BBC it would be "unusual and unexpected" for a person's IQ to rise 17 points in seven years.
"It would be easy to deliberately do badly on one IQ test," he said.
"But it would be very difficult to feign low cognition across time, different settings and multiple examiners."
Psychology tests used to evaluate a criminal's cognition typically include sophisticated traps to catch fakers.
Difficult questions that appear to be easy may be inserted to test whether people answer correctly because they feel they can allow themselves to get a simple answer right.
Other questions that look very different, but which are actually very similar, may be used to test consistency.
But some fear Atkins will not get a fair hearing, because the jury will be told the full details of the murder.
Richard Dieter, of the Death Penalty Information Center, said: "This should be an objective determination, but it will be infected by the jury's knowledge of Atkins' crime.
"The Supreme Court ruled that we should not execute the mentally retarded, it did not say it should be a balancing act with the gruesomeness of a crime."
The DPIC says courts across the country have been struggling to put procedures in place that deal with possible mental retardation cases in the wake of the Supreme Court's ruling.
Mr Dieter said that while 19 people with low IQs had been given stays of execution in Texas - the US state that puts the most people to death - they were still on death row.
"This is a symbolic case," he added."There will be a lot of attention around the country to the outcome."