Chris Watts is accused of killing his wife and two daughters

Colorado prosecutors are demanding that triple-murder suspect Chris Watts turn over DNA samples, fingerprints, palm prints and photographs of his hands in their case against him in the deaths of his pregnant wife, Shan’ann Watts, and their two young daughters.

In a motion filed Thursday, prosecutors asked the judge to compel Chris to provide them the evidence. The court has not yet ruled on the motion and the defense has until Monday to respond.

A source close to the case says prosecutors “are working very carefully. They know they can’t make a single mistake.”

Chris, 33, faces first-degree murder charges among other charges related to the killings of his 34-year-old wife and their two daughters, Celeste, 3, and 4-year-old Bella.

Under police questioning, Chris allegedly admitted he had strangled Shan’ann — but he gave a startling reason for doing so.

Shan’ann Watts and her two daughters
| Credit: Shanann Watts /Facebook

According to an arrest affidavit obtained by PEOPLE, he claimed that after he told Shan’ann he wanted to separate, he saw her strangling Celeste while Bella was “blue” and apparently lifeless in her bed nearby.

Chris purportedly said he “went into a rage” and strangled Shan’ann, the arrest affidavit states. Afterward he allegedly loaded all three bodies into his truck to conceal them at an oil work site some 40 miles east owned by his former employer.

Christopher Watts court case, Greeley, Colorado, USA - 16 Aug 2018
Chris Watts
| Credit: Joshua Polson/AP/REX/Shutterstock

Authorities aren’t buying this explanation and in charging Chris with first-degree murder in all three deaths, they have dismissed his version of events as described in the affidavit.

Chris was arrested late on Aug. 15, the day before the bodies of his wife and daughters were found. He is being held without bond in the Weld County Jail. He has not yet entered a plea.

RELATED VIDEO: Triple Murder Suspect Dad Chris Watts in Court

A source close to the investigation previously told PEOPLE, “The theory that she [Shan’ann] did it doesn’t hold any water. There is absolutely no evidence that she killed her children.”

Chris’ lawyer has not responded to PEOPLE’s requests for comment but, according to a statement from the state’s public defender’s office, their attorneys are barred from discussing ongoing criminal cases.