Pretoria, South Africa (CNN) -- Oscar Pistorius must submit to an independent psychiatric evaluation, the prosecutor in his murder trial argued Tuesday, raising the possibility of a long delay in the proceedings.
Gerrie Nel filed a motion asking the judge to require the tests, arguing that if there is any chance the defendant's mental health is an issue, the court must "err on the side of caution."
Pistorius, 27, is on trial over the killing of his girlfriend Reeva Steenkamp last year. He admits shooting her but says he thought there was an intruder in his house. He has pleaded not guilty.
The athlete's defense team is trying to show that Pistorius made a genuine mistake and responded reasonably on the night he shot Steenkamp, 29, a model and law school graduate.
Judge Thokozile Masipa will announce her decision about psychiatric observation Wednesday, she said, and adjourned court until then.
The testing would last 30 days, and Pistorius would need to wait for it to be scheduled, meaning the trial could be put on hold for months.
Pistorius' lead defense lawyer, Barry Roux, argued against new tests for his client, saying Nel's reading of the law is "unfortunate."
He mounted an impassioned case for going ahead with the trial, giving Nel an opening to begin his rebuttal with an acerbically gentle: "One thing I agree with, we shouldn't be emotional."
The court has been debating the onetime Olympic sprinter's "general anxiety disorder" this week as the trial appeared to be heading toward its end.
Psychiatrist Merryll Vorster testified Tuesday that the anxiety disorder comes out in his "excessive" concern about security, friendships lacking in depth and short-term sexual relationships.
And, she said: "People with generalized anxiety probably shouldn't have firearms."
The psychiatrist first took the stand Monday morning for the defense, going all the way back to when Pistorius was 11 months old.
Pistorius would have experienced the amputation of both of his legs below the knees at that time as a "traumatic assault" because he was too young to speak or understand what was happening to him, she said in court.
His parents then put pressure on him to appear normal, and his mother abused alcohol at times after she and Pistorius' father divorced, she said.
She raised him and his siblings "to see their external environment as threatening" and "added to the anxiety," Vorster said.
Pistorius testified last month that "Everything I learnt in life, I learned from her."
The athlete is depressed now and feeling guilt from having killed Steenkamp, Vorster said Monday.
Nel responded by comparing the athlete's mental state to post-traumatic stress disorder and saying the law required psychiatric observation.
Heading into danger
Vorster also addressed the question of why, on the night he killed Steenkamp, Pistorius took his gun and went toward the sound of what the thought was danger rather than trying to get away.
Because of his disability, she said, when he faces a fight-or-flight situation, he cannot flee, so his instinct is to fight.
Nel then pressed the psychiatrist on whether Pistorius was mentally ill and whether he could distinguish right from wrong.
She said he could.
Judge Masipa must decide whether Pistorius genuinely made a mistake or whether he murdered Steenkamp intentionally.
If she does not believe the athlete thought there was an intruder, she will find him guilty of murder and sentence him to at least 15 years in prison, and possibly life.
South Africa does not have the death penalty.
If Masipa accepts that Pistorius did not know Steenkamp was the person he was shooting at, she could find him guilty of culpable homicide, a lesser charge than murder, or acquit him, according to CNN legal analyst Kelly Phelps.
A verdict of culpable homicide would leave the sentence at Masipa's discretion.
Nel rejects the sprinter's defense that he mistakenly thought he was defending himself and his girlfriend from an intruder.
The state contends that Pistorius argued with Steenkamp before killing her.
The defense team is seeking to cast doubt on the state's case and needs to show only that there is a reasonable doubt that Pistorius meant to kill Steenkamp.
Argument or error?
There is no dispute that Pistorius fired four bullets through a door at Steenkamp in his home early on the morning of Valentine's Day 2013. Three hit her, causing devastating wounds. The final shot struck her head and probably killed her almost instantly, a pathologist testified in March.
The trial has seen Pistorius break down repeatedly, crying, wailing and sometimes throwing up as the court sees and hears evidence about Steenkamp's death.
Vorster said the athlete's physical distress was real.
When the defense is done presenting its evidence, both sides will make closing arguments, and then Masipa will retire to consider her verdict. South Africa does not have jury trials, but she is being assisted by two experts called assessors.
Pistorius is arguably the world's most famous disabled athlete, known as the "Blade Runner" for the carbon-fiber blades he runs on. He fought for -- and won -- the right to compete against able-bodied runners at the Olympics after his Paralympic success.
Sports fans worldwide saw Pistorius a symbol of triumph over physical adversity.