(CNN) -- Federal prosecutors are pushing to force the Arizona man accused of fatally gunning down six people and wounding 13 others, including U.S. Rep. Gabrielle Giffords, to submit a handwriting sample -- a request that he, thus far, has refused.
A motion was filed Monday, out of the office of U.S. Attorney Dennis Burke in Arizona, asking the court to compel Jared Lee Loughner to write out something so authorities can view his writing style.
The government wants the sample to compare with handwritten notes found in Loughner's residence that include mentions of Giffords "as well as references to guns and bullets," according to a court document. It says he has resisted such requests to date, "arguing that the court lacks authority" to force him to provide a sample.
"There being no other avenue to obtain the defendant's handwriting exemplar, the government now seeks an order to compel," prosecutors wrote in the motion.
Last Thursday, a federal grand jury returned a new indictment against Loughner in which he is charged on 49 counts -- including murder and attempted murder -- related to the shooting outside a Tucson supermarket in January.
The 22-year-old Tucson man was indicted on three counts of attempted murder, including one alleging that he tried to kill Giffords with a Glock semiautomatic handgun during the event she was hosting for constituents. After being shot through the head, the congresswoman is now undergoing rehabilitation at a medical facility in Houston, Texas.
The new indictment -- which supersedes an earlier one, which had fewer charges -- adds murder charges connected to the deaths of John M. Roll, a federal district judge, and Gabriel M. Zimmerman, a staff member for Giffords. Loughner also faces charges in the deaths of Dorothy J. Morris, Phyllis C. Schneck, Dorwan C. Stoddard, and a child, referred to in the indictment as C-T G. Nine-year-old Christina-Taylor Green was among those killed in the shooting.
Autopsy reports released Monday showed that Zimmerman, Schneck and Stoddard suffered fatal head wounds, while the three others were shot in the chest.
Loughner could face a death sentence if convicted, Burke said last week, although prosecutors have not said yet whether they will seek the death penalty.
Loughner, who is being held by authorities in Arizona, is expected to be arraigned on the new charges Wednesday in Tucson, the district attorney's office said.