CHARLESTON, S.C. —Charleston church shooter Dylann Roof says he won’t call any witnesses or present evidence while representing himself during the punishment phase of his death penalty trial, but he is working hard to keep secret potentially embarrassing evidence about himself and his family.

Just exactly what that evidence is remains a mystery. Roof, the judge and prosecutors carefully tiptoed around describing it during a hearing Wednesday. The judge has indicated that it may be allowed during the penalty phase of the trial, which starts next week.

The same jurors who convicted Roof earlier this month of killing nine black church members in a racially motivated attack will hear from Roof as well as testimony from the families of victims. At the end of the penalty phase, the panel will decide whether Roof, who is white, should be put to death or spend the rest of his life in prison.

Roof was warned by U.S. Judge Richard Gergel that being his own lawyer was a bad idea. He told Roof he has until the start of the penalty phase Tuesday to change his mind and rehire his high-powered, publicly funded defense team.

Roof spoke for less than 10 minutes of the 35-minute hearing. He told Gergel he does plan an opening and closing statement. He also told the judge he objects to prosecutors’ plans to present a photograph of evidence in the court’s possession.

Roof also wanted a jailhouse statement left out of the penalty phase and evidence that involved his mother. No specifics were given.