A forensics officer who investigated the scene of the fatal Boxing Day shooting spree in downtown Toronto was the first person to testify in the trial of a man accused of killing 15-year-old Jane Creba.

In a dramatic move, he held up one of the firearms used in the firefight that left the teen dead -- one of more than 100 pieces of evidence introduced on the first day of testimony.

The Ruger 9mm semi-automatic handgun was allegedly found on the accused  when he was arrested at the Castle Frank subway station about 40 minutes after the Dec. 26, 2005 shooting occurred.

Det. John Davidson also went over several maps of the area around Yonge and Elm Streets, where the shooting happened.

The jury also saw several photos of the crime scene where Creba, an innocent bystander, died and several others were injured in the shootout.

Davidson told the jury he collected evidence that included shell casings, a blue purse and a "pinkish pool of blood."

One photo showed the purse of Alison Creba, Jane's sister, lying in the gutter near where her sister died. Jane had been carrying it as she went to use the washroom at the nearby Pizza Pizza outlet.

The testimony came a day after the jury heard opening statements in the sensational case.

Crown attorney Kerry Hughes told the panel of jurists on Tuesday that a verbal exchange outside a downtown Foot Locker store led to the fatal gunfight. A man wearing a T-shirt with the words "Don't Snitch" on it came out of the store and approached a group of 10 men.

The Crown said a witness would testify that the man told the group he was carrying a .357-calibre gun.

The jury then heard that Creba was crouched down when she was hit, likely ducking to avoid the hail of bullets. An autopsy showed the teen was hit in the back and that the bullet exited her body through the base of her throat.

Experts believe she was likely killed by a .38- or .357-calibre firearm.

The accused, who can only be identified as J.S.R. because he was a young offender at the time of the shooting, is the first person to stand trial in the case. J.S.R., now 20, has pleaded not guilty to a charge of second-degree murder and six charges of attempted murder plus five firearm offences. 

The Crown is not alleging J.S.R. fired the bullet that killed Creba. Hughes did tell the jury that seven of the eight shell casings and two out of four bullets found on the scene came from the Ruger found on the suspect at the time of his arrest.

With a report from CTV Toronto's Chris Eby