The man on trial for killing his cellmate, then stringing his organs about their prison cell, has serious brain injuries that could have made it difficult to plan the murder or control his actions, a psychologist testified in federal court today.

William Sablan suffered two falls from at least 20 feet and a machete attack to the head while living in his native Saipan, defense attorneys have said.

Testifying for the defense, neuropsychologist Reuben Gur said scans of Sablan’s brain show that even the least damaged areas of his brain are abnormal.

"He’s not a shining light of the diaspora, to put it mildly," Gur said.

Sablan could be sentenced to death if convicted of killing fellow inmate Joey Estrella at the federal prison in Florence in 1999. His cousin and fellow cellmate, Rudy Sablan, also is charged with the murder. His trial is expected to occur after William Sablan’s.

Prosecutors say Sablan choked Estrella with a headphone cord, then slit his throat with a prison-issued razor, following a late night argument. Estrella bled to death before his body was discovered by prison guards.

While the guards waited for other staff to arrive so they could enter the cell, they began videotaping through a window in the cell door.

On the 70-minute tape, which was shown to the jury last month, the Sablans appear to be celebrating. Estrella’s abdomen has been cut open, and at one point, William Sablan reaches into the body and pulls out an organ, then shows it to the guards.

Gur testified that he watched the video and that in it, William Sablan appeared to be "totally out of control."

Defense attorneys argue Sablan cannot be held responsible for the murder because of his mental issues. Prosecutors, however, say there is no medical proof that mental problems cause a person to become violent.

The defense is expected to present its final witness Monday. The case could go to the jury the following week.