An attorney for Mahdi Hassan Ali, a teenager charged in a triple killing at a south Minneapolis grocery, is demanding police reports about a 2009 gun shop burglary because one of the stolen guns may have been the murder weapon.

The lawyer also wants reports on the arrest of the brother of Ali's co-defendant because the brother could be linked to the burglary and the reports may undermine his credibility as a witness in the murder case.

Hennepin County District Judge Peter Cahill heard arguments on Thursday. A decision is expected within a few weeks. The trial is scheduled to begin Sept. 6.

Mahdi Ali and Ahmed Ali were accused in connection with the killings committed during a robbery of Seward Market and Halal Meats on Jan. 6, 2010. Mahdi Ali is charged with shooting and killing an employee, the employee's cousin and a customer. Ahmed Ali pleaded guilty last April as part of a deal in which he agreed to testify against Mahdi Ali.

Mahdi Ali's lawyers claimed he was only 15 at the time of the killings and should not automatically stand trial as an adult, but Cahill ruled he was at least 16. The issue of his age was argued before the Minnesota Supreme Court on Wednesday.

Attorney Fred Goetz called the brother one of the prosecution's "most important witnesses" and said reports may show that he lied and omitted facts in an attempt to shift the blame to Mahdi Ali.

According to Robert Streitz, an assistant county attorney, the reports don't contain any relevant information, but he said prosecutors were willing to let a judge review them.

Staff librarian John Wareham contributed research for this report. Randy Furst • 612-673-7382