Red stains were discovered on the reinforced gloves Const. Daniel Montsion wore the day of Abdirahman Abdi's arrest, the Ottawa police officer's manslaughter trial heard Monday.

Montsion has pleaded not guilty to manslaughter, aggravated assault and assault with a weapon, charges stemming from the violent arrest outside Abdi's Hintonburg apartment building on July 24, 2016. Abdi was pronounced dead in hospital the next day.

The Crown intends to prove it was "unjustified" punches to the head that killed the 37-year-old.

The gloves bore "red stains" just above the knuckles, which are reinforced by thick carbon fibre plates, forensic investigator David Robinson told the court Monday.

Const. Daniel Montsion, right, is on trial for manslaughter, aggravated assault and assault with a weapon in the 2016 death of 37-year-old Abdirahman Abdi, left. (Supplied)

Montsion's lawyer, Michael Edelson, objected to calling them bloodstains since that hasn't been proven in court.

The gloves are manufactured by Oakley, which describes them as "tactical" or "assault gloves."

They were among the grisly exhibits entered into evidence Monday, including photos taken by Robinson outside the apartment building at 55 Hilda St.

The photos showed "red stains" on the windows, doors and brick outside the building. There was also what appeared to be a large, dried bloodstain around a storm drain, Robinson said.

Blood was also found on the uniform and baton of Const. David Weir, the first officer on the scene that day. Weir was not charged. His shoes and pants were both stained, and a red mark could be seen on a baton Robinson held up in court.

A photo of Const. Dave Weir's baton, which shows a small red stain on the shaft. (Supplied )

The Crown hasn't draw any conclusions from the evidence yet, and the defence has yet to cross-examine Robinson.

The investigator's testimony is expected to continue for the better part of this week.