Kansas City, Mo. ? Convicted serial killer John E. Robinson Sr., whose death sentences for killing two women are in constitutional limbo, is facing a new federal charge that could bring a death sentence of its own.

U.S. Atty. Todd Graves on Thursday announced that a federal grand jury had indicted Robinson, 62, of kidnapping resulting in the death of Suzette Trouten, 27, of Newport, Mich., in March 2000.

Graves said the indictment is equivalent to a federal murder charge and could be punishable by death or a life sentence. He said his office hasn’t decided whether to pursue the death penalty but added, “You can follow the logic.”

A Johnson County, Kan., judge sentenced Robinson to death in January 2003 for Trouten’s murder, as well as that of Izabela Lewicka, 21, of West Lafayette, Ind. He also received a life sentence in Kansas for the murder of a third woman, whose body was never found, and received life in prison in Missouri after pleading guilty to five other murders.

However, Kansas’ death penalty law was tossed out by the state’s highest court in December 2004, and only the U.S. Supreme Court can reinstate the death sentences against Robinson and six other men on death row.

Asked if the federal case against Robinson could be abandoned if the Supreme Court reinstates the death penalty in Kansas, Graves responded: “That’s something we’d have to consider.”

An attorney representing Robinson in his appeal of his Kansas death sentences did not immediately return a call seeking comment Thursday.

Testimony during Robinson’s trial for Trouten’s murder showed the two met over the Internet, that he asked Trouten to come to Kansas to be his sex slave and that he offered the nurse’s aide a job taking care of his elderly father while he was away on business. Investigators later found the bodies of Trouten and Lewicka stuffed in barrels on Robinson’s rural Linn County, Kan., property.

Graves focused on the job offer, saying Robinson tricked Trouten into moving to Kansas from Michigan. He said using such false pretenses was equivalent to kidnapping and that his office was involved because the trickery caused her to come through western Missouri, where he’s the U.S. attorney.

“It is certainly an expansive reading of the statute,” Graves acknowledged during a news conference, while adding that the district has successfully pushed the envelope in past high-profile murder cases. “This office and I have been aggressive in seeking the death penalty where it is appropriate. Justice seeks the ultimate penalty for the ultimate crime.”

Graves also said the charge does not violate Robinson’s constitutional protection against “double jeopardy,” or being prosecuted twice for the same crime, because the state and federal laws are considered separate entities and so Robinson committed separate offenses.

An arraignment date for Robinson hasn’t been scheduled, but Graves said authorities plan to move him from El Dorado Correctional Facility in El Dorado, Kan., to a federal prison soon.