Whether a jury convicts David Japenga of breaking the windows of three businesses in Oakland during the G-20 summit last year will depend, at least in part, on the testimony of an undercover state trooper who watched events unfold along South Craig Street.

For the prosecution, the trooper's testimony -- which will include a detailed description of the suspect's gait, sloped shoulders and shoes -- is enough.

But for the defense, who told jurors Monday during opening statements that the trooper will not be able to identify Mr. Japenga's face, it is not enough.

"What he observed is not sufficient to meet that burden beyond a reasonable doubt," defense attorney Patrick Nightingale said.

Mr. Japenga, 21, is charged with three counts of criminal mischief and one count each of possessing instruments of crime and making false identification to law enforcement.

Assistant District Attorney Kevin Chernosky told the jury before Allegheny County Common Pleas Judge Edward J. Borkowski that Mr. Japenga was responsible for breaking thousands of dollars' worth of windows at Citizens Bank, Quiznos restaurant and Irish Design Center, all on South Craig, after 11 p.m. Sept. 24.

"In its simplest form, this case is about a lack of respect for other people's property," Mr. Chernosky said.

He described Mr. Japenga as part of a crowd that started with about 150 people moving through Oakland, as undercover state Trooper Boyd Wass followed.

The crowd began to thin to about 50 people when, Mr. Chernosky said, Mr. Japenga used a U-shaped bicycle lock to break the windows at Citizens Bank.

"The crowd began cheering or chanting," the prosecutor said.

The suspect wore dark clothes, a dark bandana covering his face, gloves and a hooded sweatshirt, the trooper will testify.

The lock in his hand appeared to have orange tape around it.

Though the trooper lost sight of Mr. Japenga for two to four minutes, he caught back up with him at Bigelow Boulevard and Fifth Avenue.

There, he said, Mr. Japenga had changed into a yellow T-shirt and wore a backpack, but the trooper was able to identify him by his body shape.

When officers arrested him, Mr. Japenga's backpack contained a U-shaped bicycle lock with orange rubber around it, gloves, a black bandana and a dark windbreaker.

But Mr. Nightingale told the jurors that they should focus on the evidence the police don't have.

Though police recovered glass shards from his client's possessions, officers never matched them to any of the broken windows in Oakland.

"Wouldn't it be a reasonable step by police to see if any of those glass shards matched broken windows at Quiznos, the Irish Design Center or Citizens Bank?" he asked.

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