TORONTO - A man charged with possessing explosives ahead of last year's violence-marred G20 summit appeared incredulous while photographs of chemicals and other items seized from his house were shown in court as his trial got underway Monday.

The items were found in the basement of Byron Sonne's tony home as police executed a search warrant days before the summit in June 2010.

"They can make anything look nefarious," Sonne said as court recessed.

In the basement were, among the numerous items, various chemicals with ominous-sounding names like hexachloroethane, tetrahydrofuron and methyl hydrate.

There were also components from a microwave oven labelled magnetron.

When Crown witness Det. Const. Irvin Albrecht described a piece of garden hose attached to an air compressor as an item of interest because "it didn't make sense," Sonne spun around in court and flashed an incredulous grin.

He later said outside the courtroom the item was for cleaning his garden irrigation system.

One item Albrecht initially labelled as a home-made detonator turned out to be part of a temperature sensor.

Sonne, who is charged with possession of explosives and counselling mischief "not committed," was arrested on June 22, 2010, as he rode a city bus.

The trial proper began after Ontario Superior Court Justice Nancy Spies ruled that search warrants for Sonne's home were based on "credible and reliable" evidence.

She also said several statements Sonne made to police were voluntary and therefore admissible.

The defence had wanted the material excluded as a violation of his charter rights.

With those rulings, Sonne's trial kicked off with an agreed statement of facts that included his purchase of various chemicals.

The 39-year-old self-described security geek was seen taking photographs of the security fence that was being erected on June 15, 2010, about two weeks before the summit began, according to the agreed facts.

He had a camera and police scanner with him, court heard.

Court heard that Sonne, who was a model-rocket enthusiast, bought chemicals such as zinc oxide and five plastic jars.

He also bought potassium permanganate, which required a licence, and a rifle scope ordered from the U.S. was seized at the border although pellet-gun oil in the shipment was allowed through.

Police allege he assembled chemicals for homemade explosives and incited others to tear down the G20 security fence and surveillance cameras through his Twitter and Flickr accounts.

Among its witnesses, the Crown plans to call Crawford Anderson, a military expert in organic chemistry and improvised explosive devices, prosecutor Liz Nadeau told court.

Sonne has always maintained the chemicals he had were legal, were not combined in a dangerous way, and were actually used for making model rockets and crystals.

He also said he had been merely trying to expose flaws in G20 security, which cost hundreds of millions of dollars, and was quite public in the way that he did that.

Other items found in his home included various electronic components, an audio-level meter and camping-heater fuel.

Sonne spent 330 days in jail -- longer than any of the other 1,000-plus people arrested in connection to the summit -- before being released from custody in May.

Before his arrest he lived in a million-dollar home in Toronto's Forest Hills neighbourhood and was married to Kristen Peterson, an independently wealthy artist.

She was also arrested, but charges against her were dropped.

Now he's in the middle of divorce proceedings and living with his parents.