The "Baby Kate" murder trial in Ludington has entered a second week -- jurors were warned by the court it could last three-weeks.

Sean Phillips is charged with murder in connection with the disappearance of daughter Katherine Phillips. "Baby Kate" was last seen on June 29, 2011.

Her mother, Ariel Courtland testified last week she last saw Katherine in a car seat in the back of Sean Phillips' car. He was driving away from Courtland's Ludington apartment. Police conducted numerous searches for Katherine.

She has never been located.

On Monday, Oct. 3, jurors heard what Sean Phillips admitted to shortly after Courtland called 911 to report Katherine had been taken.

Earlier: Ludington officer says he found 'Baby Kate's' clothes in father's pocket

Officer Tony Custer with the Ludington Police Department was on the stand for much of Monday morning.

Custer told jurors he and other officers were looking for Sean and Katherine. Sean Phillips' whereabouts was unknown for about two-hours after Courtland called 911.

Sean Phillips eventually returned a voice message police left on his cell phone. Phillips told police he was at his parents' home. He was instructed to remain at that location.

Sean Phillips in court on Tuesday, Sept. 27, 2016.

When Custer arrived, Sean said Katherine was with Courtland. Saying specifically "it" is with Courtland, according to Custer.

Police already knew at that point Courtland placed Katherine with Sean. After further questioning, Sean Phillips admitted to Custer that he was not telling the whole truth, but he didn't offer Custer any further information on what the whole truth was.

"In my mind this just went from a well-being check to something much worse," Custer said.

Police found Kate's clothes stuffed into the pocket of Sean's shorts, and her car seat and diaper bag in the trunk of Sean's car.

Custer also testified he recovered a baby bottle that looked like it had recently been emptied by a child in the trunk of the vehicle.

Police later noticed, thanks to hospital surveillance video, that at some point after Sean Phillips left Courtland, but before police arrived at his home, he changed shoes. Police found the other pair of shoes in Sean Phillips' bedroom.

"And there was dirt embedded into the suede of those shoes," Custer said.

The dirt may be an indication that Sean Phillips at some point that day was in a dirty or muddy location. A second police officer Monday told jurors about several unsuccessful searches of both land and water to find "Baby Kate"

The trial is expected to include a letter Phillips wrote from jail. It's in that letter Sean Phillips wrote he put Kate in a "peaceful place."

Jurors also watched the hour-long interview police made with Sean Phillips on June 29, 2011.

A detective gave Sean Phillips repeated opportunities to reveal where Kate was. Sean Phillips once said Ariel had her. Another time, he told police one of Courtland's friends might have his daughter. He told the detective he last saw Katherine outside Courtland's apartment.

Courtland, Sean Phillips said, was walking into the apartment building with Kate in a car seat.

Sean Phillips never told police where Kate was -- he never admitted doing anything to her.

The trial is expected to include 60 witnesses.

Sean Phillips is already serving a 10-year prison sentence for the unlawful imprisonment of Katherine. A jury reached that conclusion in 2012.

The trial resumes Tuesday morning in Ludington.