By Jessica Dye

NEW YORK, Nov 21 (Reuters) - A convicted cop killer who escaped death row in 2010 is trying to beat the federal death penalty for a second time by claiming on the resentencing that he is mentally retarded.

Ronell Wilson, 30, was sentenced to death by a jury in 2007 for murdering two undercover New York Police Department officers posing as gun buyers in Staten Island. The 2nd U.S. Circuit Court of Appeals vacated his sentence in 2010, finding that prosecutors violated his constitutional rights by, among other things, telling jurors his decision to go to trial indicated a lack of remorse and refusal to accept responsibility for the crime.

The court remanded the case for resentencing and the U.S. Attorney last year said it would once again seek the death penalty. New York abolished the death penalty in 2004, but Wilson's was a federal death sentence, the first in the state since 1954.

At a hearing starting Monday, Wilson's lawyers are scheduled to argue to U.S. Judge Nicholas Garaufis that Wilson is mentally retarded and that executing him would run afoul of the U.S. Supreme Court's 2002 ruling in Atkins v. Virginia. In Atkins, it was ruled that "the mentally retarded should be categorically excluded from execution" because doing so would violate the Eighth Amendment's ban on cruel and unusual punishment. Wilson is being sentenced under the Federal Death Penalty Act, which bars the execution of mentally retarded prisoners but does not define mental retardation.

Wilson, a member of a gang called the Stapleton Crew whose street name was Rated R, was convicted for the execution-style slayings of two undercover officers who were part of a sting operation targeting the gang. When officers arrested Wilson several days later, they said he was carrying rap lyrics he had penned about the officers' murders.

In a February letter to Garaufis, Wilson's lawyers said that a "preliminary investigation" had indicated their client was mentally retarded. Since then, Wilson has undergone a battery of psychiatric tests by experts from both sides. The findings have not yet been made public, and both sides declined to comment on the case or the evidence they will present during the hearing.

Wilson's mental condition was brought up briefly during his first sentencing proceeding in 2007, although his prior defense counsel did not raise an Atkins claim. They told jurors that Wilson had an IQ in the high 70s and said he had been hospitalized for psychiatric problems several times as a child.

Garaufis, relying on criteria in Atkins, in June set forth factors he will use to evaluate Wilson's claim, including his IQ score, his adaptive functioning or ability to perform life skills like holding a job and whether his alleged condition began to manifest itself before his 18th birthday.

ATKINS CLAIM

If Garaufis grants the Atkins claim, Wilson would be sentenced to life in prison for his conviction. If the judge rejects the claim, a jury would once again decide whether he should be sentenced to death.

Courts nationwide have granted dozens of Atkins claims since the Supreme Court's 2002 decision, said Cornell Law School professor John Blume, who tracks death penalty cases. A patchwork of state and federal laws defining what qualifies as "mentally retarded," however, has made application of the standard uneven.

About seven percent of the more than 3,000 death row inmates across the country pursue Atkins claims, according to a 2009 analysis from Blume and his colleagues at Cornell. Of these, roughly four out of 10 claims result in a determination of mental retardation, the analysis found.

Typically, Atkins claims are raised and decided before the guilt phase of the trial, but they can also come after post-conviction appeals, like Wilson's.

The more borderline the alleged retardation, the more contentious the Atkins determination typically is, Blume said. For instance, a defendant with an IQ below 40 could be fairly easily categorized as retarded, but someone with an IQ as high as 70 or 75 could also qualify.

Blume said it was difficult to predict how Wilson's claim would fare. But Garaufis has blocked off more than 10 days over three weeks, including some Saturdays, to hear evidence on the Atkins claim, indicating that Wilson may be in for a lengthy battle.

The case is U.S. v. Wilson, U.S. District Court for the Eastern District of New York, No. 04-1016.

For the U.S.: James McGovern, Celia Cohen and Shreve Ariail.

For Wilson: Colleen Brady, David Stern and Michael Burt.

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