But six months into the investigation of a most unusual murder, Avigliano's confidence is flagging. If the killing of Geetha Angara isn't a perfect crime, it's shaping up to be awfully close.
"I'm not going to gild the lily. We're still where we were at the start," Avigliano said in a recent interview. "It's a tough, frustrating case."
It's a frustrating turn of events in a case that, at the outset, appeared solvable.
The plant, which provides drinking water for 800,000 people in 17 northern New Jersey communities, is ringed by a 10-foot fence. Cameras cover the main gate and part of the perimeter.
Investigators quickly suspected only a co-worker could have killed Angara, limiting the pool of suspects. But progress has proved elusive since.
The underground tank from which the woman's body was retrieved contains water treated with chlorine, a disinfecting agent that over time destroys fingerprints and DNA evidence.
If such evidence existed, it was gone by the time divers found Angara, more than 24 hours after her killer placed her there.
The hunt for a motive, a key element in solving any crime, continues. Avigliano said detectives have found nothing to contradict early characterizations of Angara as a professional, well-liked employee. She had no reported run-ins with colleagues, no illicit relationships.
"There's nothing that shows animosity between her and the people there," the prosecutor said. "It appears to be a random act."
Investigators are now exploring another long shot, but one the prosecutor said makes sense given Angara's role in ensuring water quality. Avigliano said his office was in the process of asking the federal Environmental Protection Agency to review the facility's water records to search for signs of tampering.
While Avigliano has not disclosed precisely how Angara was rendered unconscious, he said her body showed no signs she had been battered or struck. No weapon was used. Asked if Angara had been choked, the prosecutor declined comment.
Rao said her sister had no problems at the water commission, and she finds it chilling that Angara's killer, as authorities suspect, continues to work there.
"It's very, very troubling to me that someone who could do this would continue to go to work every day, with access to drinking water for so many people," Rao said. "I wouldn't want to drink that water. If you could kill somebody, what else could you do?"