Pleau, of Providence, is one of three people charged in the shooting death of David Main, 49, on Sept. 20, 2010.
Prosecutors say that two days before the killing, Pleau and Jose A. Santiago and Kelley M. Lajoie, both of Springfield, Mass., hatched a plot to rob Main of the receipts from the Shell station where he worked.
Prosecutors say Lajoie acted as a lookout while Santiago drove the getaway truck.
Pleau allegedly wore a mask and shot Main several times outside a Citizens Bank branch, then made off with about $12,000 in deposits.
The three were charged in state court in October 2010, then indicted by a federal grand jury that December. Lajoie has pleaded guilty to robbery and other charges and is awaiting sentencing. Santiago is charged with conspiracy, robbery affecting commerce and a weapons charge. A not guilty plea has been entered on his behalf.
Pleau last week asked U.S. District Judge William Smith to dismiss the death penalty portions of his indictment, arguing in part that it is unconstitutional and that it is not allowed in the state of Rhode Island. The judge has not yet ruled.
Associated Press writer David Klepper contributed to this report.