by KYW's Tony Hanson

A Philadelphia jury has heard opening statements in the trial of man, now 18, charged with killing a 16-year-old boy two years ago for his brand new dirt bike (see previous stories).

Prosecutor Jennifer Selber says defendant Eric Smith (above), who was also 16 at the time of the killing, was in Tacony Creek Park and armed with a gun when he heard a dirt bike coming.

According to Selber, Smith decided he would take the dirt bike and kill whoever was on it. Victim Luis Navarro (right) was shot three times in the back.

Selber says defendant Smith was with a friend when he committed the murder and later confessed to two other friends, saying he had "caught a body."

The victim’s father, also named Luis Navarro, testified on Wednesday that he and the boy's mother had given the dirt bike to their son just four days before his murder -- because he was doing so well and wanted it so much.

The father, fighting back tears, says he put a helmut on his son so he would be safe if he fell. But a short time later the teen was dead, shot to death during the robbery.  The sporty bike, with a bullet hole through the front fender, was brought into court for identification.

But the defense attorney has told the jury that Smith is presumed innocent, and the defense has challenged the credibility of the prosecution’s witnesses, saying they have motives to lie because they had been suspects in the murder.