One of Allen “Lil Boo” Robertson Jr.’s attorneys said Monday he’ll ask the state’s top court to review a judge’s refusal to disqualify himself from deciding whether the condemned killer is mentally impaired and ineligible for execution in the brutal New Year’s Day 1991 stabbing deaths of an elderly Baton Rouge couple.

Robertson’s lawyers claim state District Judge Mike Erwin, who presided over Robertson’s 1991 and 1995 capital murder trials, has demonstrated he cannot be fair and impartial in making such an important life-or-death decision.

East Baton Rouge Parish prosecutors dispute that claim.

Robertson’s attorneys filed a motion in October asking Erwin to recuse himself, but the judge denied the request last month.

Gary Clements, one of Robertson’s lawyers, said the Louisiana Supreme Court will be asked to review and reverse Erwin’s ruling, which came without written reasons.

Robertson’s attorneys argued in their recusal motion that the judge made the following sarcastic statement during an April 2014 hearing: “I’m sure pretty much everybody on death row is retarded now.”

Prosecutors opposed the motion and contended that the 47-year-old Robertson is simply trying to delay his inevitable execution for the slaying of Morris and Kazuko Prestenback, 76 and 71, respectively, in their Dalton Street home.

A psychologist hired by Robertson’s attorneys testified in late 2013 that Robertson is mildly mentally retarded, while a psychologist appointed by Erwin testified last spring that Robertson falls within the borderline intelligence range but is not mentally retarded or intellectually disabled.

Intellectual disability is now the term used to describe what was formerly called mental retardation.

The U.S. Supreme Court in 2002 barred the execution of mentally retarded inmates.

The hearing to determine whether Robertson is intellectually disabled was scheduled to resume for several days this week, but it was delayed. New dates have not been set.

Robertson was 23 when he killed the Prestenbacks while burglarizing their home for money to buy drugs. Morris Prestenback was stabbed repeatedly in the head, face and chest with a butcher knife from the couple’s kitchen. Kazuko Prestenback was stabbed in the chest and back.

The state Supreme Court reversed Robertson’s first conviction and death sentence in 1994 because of a jury-selection problem.

Erwin declined to overturn Robertson’s 1995 conviction and death sentence in 2008, and also rejected Robertson’s request for a hearing on his mental retardation claim because the judge said he observed him during both trials and saw no signs of a mental defect.

The state high court, though, ordered Erwin to hold a hearing.