By Don Bolding and Jim Forsyth
FORT HOOD, Texas (Reuters) - A military judge ruled on Tuesday that a terrorism expert may testify in the trial of the accused Fort Hood gunman, Army psychiatrist Nidal Hasan, but he will not be allowed to weigh in on whether Hasan is a terrorist.
The testimony of Evan Kohlmann, who has taken the stand at the trials of a number of al Qaeda-linked suspects, could be key in determining whether Hasan will face the death penalty for the murders of 13 people during a shooting rampage at the military post in November 2009.
Prosecutors are hoping to establish that the deadly rampage was premeditated, proof of which is essential under the Uniform Code of Military Justice. Premeditated murder carries a potential death penalty.
Military judge Colonel Tara Osborn ruled at a pre-trial hearing that Kohlmann may take the stand to talk about the characteristics of a terrorist but that he may not discuss whether Hasan has those characteristics.
That is still a victory for the prosecution, said Jeffrey Addicott, a former Judge Advocate General and director of the Center for Terrorism Law at St. Mary's University in San Antonio.
"As long as he is able to describe the motivation - radical Islam - you don't need to label Hasan as a terrorist," Addicott said.
Hasan, who has used a wheelchair since he was paralyzed from the chest down by bullet wounds inflicted by civilian police officers during the shooting, appeared at the hearing wearing Army fatigues.
Prosecutors told Osborn on Tuesday that they will seek a motion compelling Hasan's relatives and associates to appear in court.
"I intend to chase them around in the dark and have them served" with a subpoena, lead prosecutor Colonel Mike Mulligan told Osborn.
Prosecutors were also seeking to learn more about defense witnesses, and the judge instructed defense lawyers to prepare a synopsis of what their witnesses will say, to be shared with prosecutors.
"They've been interviewed by the FBI - we know what they will say," defense lawyer Lieutenant Colonel Kris Poppe said during the hearing. "The government just wants to see our case."
Opening arguments in Hasan's court martial are expected to begin in July after selection of the jury, set to begin in late May.
(Editing by Corrie MacLaggan, Gunna Dickson, Cynthia Johnston and Tim Dobbyn)