An Idaho police chief insisted the killings of four college students isn't going cold, but a police expert said he's 'concerned' that investigators haven't solved the case yet

• The police chief probing the killings of four Idaho students insisted the case is not going "cold."
• But a police expert told Insider it's "concerning" that the crime still has not been solved.

The police chief leading the murder probe into the killings of four University of Idaho students has insisted the case is not going "cold," but a police expert told Insider that it's "concerning" that investigators have not yet solved the heinous crime.

"At this moment, I'm very concerned about the progress of the case," Joseph Giacalone, a retired NYPD sergeant and adjunct professor at New York's John Jay College of Criminal Justice, told Insider.

It's been almost four weeks since the four friends were stabbed to death at an off-campus home in the small city of Moscow, Idaho — and police have made no arrests or publicly identified any suspects, leaving the community on edge and the victims' families frustrated.

"The longer this goes, the worse it gets, because you're going further out from the distance between you, the police, and your suspect," Giacalone, a 20-year NYPD veteran and former commanding officer of the department's Bronx Cold Case Squad, said on Wednesday.

The weeks between now and the November 13 killings have "allowed the suspect to get rid of evidence, get rid of the clothes or get rid of whatever they had with the knife," Giacalone said.

Police investigating the slayings have still not found the weapon used in the attack, but a local coroner said she believes it to be a "pretty large knife."

Despite there being no arrests made or suspects named, Moscow Police Department Chief James Fry insisted during an interview with Fox News this week that the case "is not going cold."

"We have tips coming in. We have investigators out every day interviewing people. We're still reviewing evidence," Fry said during the interview, which aired on Tuesday. "We're still looking at all aspects of this, and I said early on that no stone will go unturned. And I mean that. We are going to continue."

"This case is not going cold," vowed Fry, who became emotional during the interview.

Giacalone told Insider that a case only goes "cold" when there are "no more active or hot leads," and said something like DNA is considered "an active lead."

"It's important right now to make sure that [investigators] get some headway with all [forensic] test results that they have," said Giacalone, who told Insider this week that the killer responsible for the slayings likely left DNA behind, but the college house where the crime happened could complicate the probe.

Giacalone added, "When all active leads go cold, that's when the case goes cold — it can happen in a day, or it can happen in a year."

The Moscow Police Department and a local coroner have said that friends Kaylee Goncalves, 21, Madison Mogen, 21, Xana Kernodle, 20, and Ethan Chapin, 20, were attacked — likely while sleeping — in the early morning hours of November 13 following a night out.

As of Tuesday, detectives have received more than 2,645 emailed tips, 2,770 phone tips, and 1,084 digital media submissions. More than 100 pieces of physical evidence have been collected and about 4,000 crime scene photos have been taken, police have said.

"At this point, you would hope that they have either a suspect or a group of suspects that they're trying to exclude," Giacalone said.

However, the former NYPD homicide investigator noted that just because police publicly state that no suspect has been identified, "it means absolutely nothing."

"Sometimes in the police department, you have to play poker where you're just bluffing," he said. "'Yeah, we have nothing. We know nothing. We do nothing' — and then, boom, pull the rabbit out of a hat."