Defence and prosecution psychiatrists disagree on the sanity of a New Zealand post graduate student accused of murdering his wife in New York state.

Blazej Kot, 25, an Auckland University graduate, had no major psychiatric disorder when he killed his wife, Caroline Coffey on June 2, last year, a psychiatrist testifying for the prosecution, Dr Gary Horowitz told Tompkins County Court.

But for the defence Dr Rory Houghtalen said Kot suffered from paranoid delusions and feared that he was being tested by unseen forces, and thought he could end the testing.

Kot has been accused of murdering Dr Coffey, tampering with evidence, and setting fire to an apartment in Ithaca, a New York state university town.

Kot's lawyer Joe Joch argued his client killed because he was suffering from an extreme emotional disturbance, a defence under state law that can reduce a murder charge to manslaughter.

Dr Houghtalen testified that Kot, who he interviewed four times after the killing, was trying to conceal his thoughts in the first two interviews and that it was unusual for someone with a "toxic mental state" to show symptoms all the time, WENY TV reported.

After the defence rested rested its case, the prosecution called Dr Horowitz as a rebuttal witness.

He told the court Kot was stressed and unhappy at the time of the killing but there were no signs of any major psychiatric disorder.

This doctor said that tapes of Kot's psychiatric interviews showed he had more self-awareness than someone who was insane, WBNG TV reported. Kot's mention in his first interview last July, of feeling like he was being tested, was in a self-reflective, non-delusional way.

And Dr Horowitz said Kot saw his wife as a barrier to his success.

The case is expected to go to the jury as early as this weekend (NZ time).