A Manitoba judge has agreed to let lawyers for accused letter bomber Guido Amsel cross-examine a Winnipeg police officer who prepared a DNA warrant that helped secure his arrest.

But Judge Tracey Lord said Tuesday that cross-examination of the officer will be limited to questions about his knowledge of an Aug. 25, 2015 RCMP lab report that tested negative for the presence of explosive residue on Amsel's hands.

Amsel, 51, is charged with five counts of attempted murder and several explosives offences.

Amsel was arrested in July 2015 after letter bombs were delivered to his ex-wife and two law firms. Two of the letter bombs were safely detonated, but lawyer Maria Mitousis lost her right hand and suffered several other injuries when a package she was holding exploded.

Defence lawyers argued a police officer who swore an affidavit included in the DNA warrant and a number of "sub-affiants" failed to provide relevant information regarding swabs taken from Amsel's hands to test for explosive residue, and an FBI handwriting analysis.

Court heard an initial swab test of Amsel's hands yielded a presumptive positive result for explosive residue. A subsequent test at the RCMP lab, which was not noted in the police affidavit, could not confirm the presence of explosive residue.

Defence lawyers argued exclusion of the report and other relevant information could be evidence of an attempt to deceive the court.

Lord declined the defence request to cross-examine the sub-affiant officers, ruling questioning them would be of "little probative value."

The defence is set to cross-examine the officer Wednesday. The hearing is part of a week-long defence motion seeking to toss out the DNA warrant.

The trial proper is set to begin hearing witness testimony Oct. 25.