Testimony has started in the trial of a 13-year-old boy charged with murder in the fatal stabbing of a 9-year-old boy on a playground in western Michigan.

Dani Verkerke told a jury Tuesday that her son, Michael Connor Verkerke, introduced the older boy as his "new friend" the day Michael was slain a year ago in Kentwood, near Grand Rapids.

The two didn't know each other before the younger boy was approached at the playground and stabbed after falling off a slide.

The Associated Press isn't naming the defendant because of his age. He was 12 at the time and is designated as an adult in the juvenile court system. That means he would be sentenced as a juvenile if convicted then resentenced as an adult at age 21.