Krasner said Muhammed, 31, has been held in the medical unit of the city prisons since his Feb. 10 arrest and is under suicide watch.
"I think it's important to do this now since the death penalty may be asserted in this case," Krasner told Municipal Court Judge David C. Shuter.
Shuter agreed and postponed the preliminary hearing for the two men until April 3. Defense attorney Jack McMahon, the lawyer for Scott, 30, said he would ask to have the men tried separately if Muhammed is unable to participate in the April 3 hearing.
Muhammed is accused of being the gunman who, with an accomplice, went to rob Lorena's Grocery at 850 N. 50th St. on Sept. 6, shortly before the store's 8 p.m. closing.
After bursting into the family-owned grocery, the gunman shot and killed owner Porfirio Nunez, 50, and then his wife, Carmen, 44, and her sister, Lina Sanchez, 48.
Police said the robbers did not shoot Nunez's two teenage daughters, who hid behind a counter. The robbers fled without taking any money.
Assistant District Attorney Edward Cameron confirmed that his office was considering seeking the death penalty.
Cameron also told the defense lawyers that both men had been identified from photo arrays by one of the Nunez daughters and one of the men had been identified by the other.
For months after the killings, there were rewards offered and regular public pleas for information leading to the arrests of the robbers.
In January, police officials organized a task force of detectives to look anew at the case. In early February, detectives learned that the killings could be linked to a robbery last August of a Southwest Philadelphia corner store and the earlier shooting of a North Philadelphia store clerk.
Surveillance footage of the Southwest robbery, at the Jaquez Grocery at 62d and Reedland Streets, provided investigators with clearer images of the assailants' faces and ultimately led to Muhammed's house in the 6200 block of Reedland Street, a block from Jaquez Grocery.
Contact Joseph A. Slobodzian at 215-854-2985, email@example.com, or follow on Twitter @joeslobo.