The sources, who spoke on the condition of anonymity, said the paper toll ticket could be an important clue in a case that remains a mystery.
The ticket also suggests another possibility for investigators - that someone other than Luna was driving his silver-colored Honda Accord when it entered and left the Pennsylvania Turnpike. Luna's car had an EZ Pass card, which meant it could have entered the highway without stopping to take a toll ticket, something that a driver unfamiliar with the vehicle might not have known.
One law enforcement source told The Sun that the large amount of blood found on the floor of the back seat of Luna's car also was consistent with the theory that Luna was lying wounded and dying as his attacker drove, looking for a place to abandon the body and car.
Authorities still had not identified yesterday a suspect in Luna's slaying, however, and continued reviewing details of Luna's personal life for possible clues to his death. Investigators have not found evidence linking the slaying to Luna's work.
Luna, who was married with two young sons, had worked as a federal prosecutor in Baltimore for the past four years. He was buried Monday.
Maryland U.S. Attorney Thomas M. DiBiagio, speaking to reporters about an unrelated indictment, declined to comment yesterday on the Luna investigation. A spokesman for the FBI's Baltimore field office said investigators were continuing to pursue all leads.
As the investigation approached the two-week mark, sources indicated that the U.S. attorney's office for the Eastern District of Pennsylvania was expected to play a more prominent role in the probe and could assume responsibility for it in the near future. The case also could be turned over to a state prosecutor and pursued as a local homicide investigation.
A spokeswoman for DiBiagio declined to comment on that issue. In Philadelphia, a spokesman for U.S. Attorney Patrick L. Meehan said, "We're here, at this point, to assist the investigative agencies.
"Our primary focus is helping solve the case," said Rich Manieri, the spokesman for the federal prosecutor's office in Philadelphia.
The jurisdictional question is important because the investigation is focused primarily on Delaware and Eastern Pennsylvania, not Maryland. On the night before he was found dead, Luna had traveled from his home in Elkridge to the federal courthouse in downtown Baltimore to complete paperwork for an expected plea agreement the next morning.
Authorities think he left the courthouse about 11:30 p.m. and drove toward Philadelphia willingly. Electronic records indicate that Luna withdrew $200 from an automated teller machine in Newark, Del. His credit card records also reflect a gasoline purchase at a Sunoco gas station in King of Prussia, Pa., along the Pennsylvania Turnpike.
A gas station attendant reported last week seeing someone who looked like Luna enter the station's convenience store about 3 a.m., but authorities have discounted that account and have not found evidence on the store's grainy surveillance video suggesting Luna was inside.
It was unclear yesterday exactly where Luna's car entered the Pennsylvania Turnpike. It was also unclear whether the blood evidence found on the turnpike toll ticket at Ephrata belonged to Luna or a second person.
When his car was discovered in Lancaster County, Pa., investigators identified blood and DNA evidence from a second person - possibly Luna's attacker, who could have been cut in a struggle over the knife used in the attack. Investigators have not found a weapon. They have said Luna's wounds appear to have been from a small blade, possibly a penknife.