A military judge blocked several key pieces of evidence Monday that prosecutors said would explain the mindset of the soldier accused in the 2009 shooting rampage at Fort Hood, including his belief that he had a “jihad duty” to carry out the attack.

Prosecutors had asked the judge to approve several witnesses and various evidence to support what they allege motivated Maj. Nidal Hasan to kill 13 people and wound more than 30 others at the Texas military base. But the judge, Col. Tara Osborn, blocked nearly all of it.

Osborn also strongly urged Hasan to forgo representing himself and allow trained attorneys to take over.

She told Hasan she believed he’d be better off with a lawyer who would know the rules for military trials, such as when to raise objections and how to spot issues for appeals.

Hasan acknowledged that Osborn had relayed such advice “repeatedly,” but he insisted on representing himself.

As for the evidence, Osborn barred any reference to Hasan Akbar, a Muslim soldier sentenced to death for attacking fellow soldiers in Kuwait during the 2003 Iraq invasion. Prosecutors wanted to prove that Hasan, an American-born Muslim, wanted to carry out a “copycat” attack, but the judge said introducing such material would “only open the door to a mini-trial” of Akbar.

She also said such evidence would result in a “confusion of issues, unfair prejudice, waste of time and undue delay.”

The judge said prosecutors also couldn’t introduce three emails, ruling that the needed redactions would make them irrelevant. The contents of the emails were never disclosed, but the FBI has said Hasan sent numerous emails starting in December 2008 to Anwar al-Awlaki, a radical U.S.-born Islamic cleric killed by a drone strike in Yemen in 2011.

The judge also told prosecutors that they couldn’t cite Hasan’s interest years ago in conscientious objector status and his past academic presentations. Osborn said such evidence was too old and irrelevant.

However, the judge will allow evidence about Internet searches on Hasan’s computer close to the time of the attack and websites that Hasan had listed as “favorites.” Osborn said that information was more timely.

Military prosecutors opened the trial by saying they would show that Hasan felt he had a “jihad duty,” referring to a Muslim term for a religious war or struggle. After calling almost 80 witnesses during the past two weeks, prosecutors said Friday that they would begin tackling the question this week.

Monday’s ruling frustrated Reed Rubinstein, an attorney representing victims and their relatives in a civil lawsuit against the U.S. government. He said only in an “alternative universe” could the emails excluded by Osborn be irrelevant, and he blamed the government for dragging out Hasan’s case and making the evidence now too old to be considered.

Prosecutors indicated Friday that they had between 15 and 25 witnesses left, though it wasn’t immediately clear how Monday’s ruling would shorten prosecutors’ case. Either way, Hasan was expected to get his chance to defend himself as early as today or Wednesday.

Hasan signaled before trial that he had just two witnesses, but he has remained largely silent during the first two weeks of his trial. During a barely one-minute opening statement, he told jurors that evidence “will clearly show that I am the shooter,” but he said it wouldn’t tell the whole story.

The Army psychiatrist briefly questioned a witness Monday. Of the prosecution’s more than 80 witnesses called so far, Hasan has questioned only three.

Hasan faces numerous charges of murder and attempted premeditated murder. If convicted, he could face the death penalty.