Photo: Contributed

Every reveller on the B.C. legislature's front lawn on Canada Day 2013 would have been in danger of "death or grievous bodily harm" had a trio of shrapnel-packed pressure-cooker bombs successfully gone off, a police explosives expert told a court.

"I would not feel comfortable having someone on Belleville Street or on the sidewalk there by the waterfront knowing that those devices were going to explode," Const. Peter Cucheran told jurors on Tuesday.

Belleville Street runs immediately in front of the legislature and is about 150 metres from the alleged detonation sites.

The jury has already heard the bombs were inert and were built and hidden on the legislature grounds by John Nuttall and Amanda Korody while the RCMP conducted an undercover operation.

Both have pleaded not guilty to four terrorism charges related.

The minimum safe standby distance for a more-than-two-kilogram C4 explosive would be more than 250 metres, Cucheran told jurors.

Pressure waves emanating from the explosion would have been enough to cause death or serious injury within 30 metres, said Cucheran.

"Blast pressure is what we would consider the most dangerous in close proximity to an explosion because it can move through you and simply turn your organs into mush," he added.

Footage played in B.C. Supreme Court on Tuesday showed Mounties detonating the same model of homemade pressure-cooker explosive that Nuttall and Korody are accused of building for their alleged plot.

Cucheran narrated the scene to the jury as a pressure cooker packed with nails, metal washers and more than two kilograms of C4 plastic explosive obliterated a surrounding ring of plywood boards.

The detonation took place inside a sand-filled compound lined with two tiers of concrete blocks, located at a police explosives range in the Vancouver area.

When asked, Cucheran said that he couldn't recall whether he saw any shrapnel embedded in the quarter-inch sheets of plywood in the aftermath of the staged explosion.

"Everything that I saw had holes through it," he said.

All that was left in the compound, which was caked with dirt following the blast, was a smoking crater and wood debris.

Jurors watched a second video of a pressure cooker filled with gunpowder exploding. Court heard previously Nuttall telling an undercover officer that he would use gunpowder to build a bomb if he failed to acquire C4.

The blast from the second explosive did not appear as powerful as the C4 bomb and failed to even topple the surrounding plywood boards.