Lawyers for the Idaho killings suspect have a 'Herculean task' defending him from DNA, cellphone, and other evidence, police expert says

• Lawyers for the Idaho killings suspect have a "Herculean task" defending him, a police expert said.
• "He's in trouble," a retired NYPD sergeant told Insider of 28-year-old suspect Bryan Kohberger. 
• A police affidavit was unsealed this week detailing what led authorities to arrest Kohberger.

Attorneys for the man accused of stabbing to death four University of Idaho students have a "Herculean task" while defending the suspect from the mounting evidence that authorities have against him, a police expert said. 

"He's in trouble," retired New York Police Department sergeant Joseph Giacalone told Insider on Friday of 28-year-old suspect Bryan Kohberger following the release of a detailed police affidavit. 

Kohberger, a Ph.D. student in the criminal justice program at Washington State University, has been charged with four counts of first-degree murder and one count of felony burglary in connection to the November 13 slayings in Moscow, Idaho. 

The affidavit unsealed on Thursday revealed new details about the night of the killings and what led to authorities' arrest of Kohberger in his home state of Pennsylvania in late December.

Authorities identified Kohberger as a suspect through DNA discovered at the crime scene — an off-campus rental home where three of the victims lived — cellphone records, and surveillance footage of a car, according to the affidavit. 

"Let's put it this way, his defense team has a Herculean task ahead of themselves," said Giacalone, a 20-year NYPD veteran and former commanding officer of the department's Bronx Cold Case Squad. 

Giacalone, an adjunct professor at New York's John Jay College of Criminal Justice, added, "They are going to have to fight cell phone evidence. They're going to have to fight the video surveillance and the DNA, and God knows what else [the police] have that we don't know about yet."

At the three-story home where Kaylee Goncalves, 21, Madison Mogen, 21, Xana Kernodle, 20, and her boyfriend Ethan Chapin, 20, were killed, investigators discovered DNA on a tan leather knife sheath on a bed near two of the victims that they linked to Kohberger, the affidavit says. 

Giacalone, who read the 18-page affidavit twice, called that piece of evidence "phenomenal."

"They're not relying on DNA that's found on the floor, on the wall," Giacalone said, explaining, it's "something specific to the weapon that was used to kill these kids." 

The weapon used in the killings has still not been found, and police have not yet provided a motive.

Additionally, cell phone records obtained by police showed that Kohberger's phone was near the three-story home where the victims lived with roommates at least a dozen times between June and before the early morning killings, according to the affidavit. 

"It looks like he was staking out this place," Giacalone said.

The records also showed that Kohberger's cell phone pinged around 2:42 a.m. on the night of the killings in Pullman, Washington, where Kohberger lived a short distance from the University of Idaho students. 

The phone dropped off the network at 2:47 a.m. and reconnected at 4:48 a.m. south of Moscow, according to the affidavit. Investigators believe the four college friends were killed between 4 a.m. and 4:25 a.m., the affidavit says. 

The affidavit also said that surveillance footage captured multiple sightings of a white sedan that police believe to be Kohberger's Hyundai Elantra near the students' home between 3:29 a.m. and 4:20 a.m. 

At around 4:20 a.m., the sedan was seen leaving the area "at a high rate of speed," according to the affidavit.

Cell phone records obtained by police also imply that the suspect returned to the crime scene hours later at 9 a.m., before anyone called 911, the affidavit says.

In addition to DNA evidence, investigators already have two of what Giacalone calls "the three forensic horsemen" — cell phone records, internet records, and surveillance video.

The phone records and the surveillance footage of the car "played a key role in to putting [the suspect] in and around the crime scene," Giacalone said. 

And Giacalone noted, "there's so much still we don't know" about what other evidence investigators may have.

Kohberger's public defender did not immediately respond to a request for comment by Insider on Friday.

The suspect has said through a lawyer who represented him in Pennsylvania that he believes he will be "exonerated."