▶ Watch Video: Twist in Mollie Tibbetts murder case could put conviction in doubt

Sentencing in the case of the killing of 20- year-old Mollie Tibbetts was supposed to be finished by today, but it was postponed after the defense said it had new evidence. 

Cristhian Behena Rivera was scheduled to be sentenced to life in prison yesterday for the 2018 murder of the University of Iowa student. Instead, a judge is now considering possible new evidence. The defense argues that the new evidence supports Rivera’s testimony that he was kidnapped and framed for her murder.

Attorneys for Rivera said two new witnesses say a man confessed to killing Tibbetts and say she was murdered after she was abducted and held for sex trafficking at a home that could be connected to other disappearances in the area.

After his arrest, Rivera led investigators to her body in a cornfield and told them he murdered Tibbetts. But at his trial in May, Rivera, a Mexican national, testified he was kidnapped at gunpoint by two men and forced to drive them to a rural road where he said they passed Tibbets jogging. He said a man got out of his car with a knife, stabbed Tibbets to death, and put her body in the trunk. Rivera said the men threatened to hurt his family before leaving him to dispose of her body. The jury found Rivera guilty in Tibbett’s murder.

Both witnesses came forward to authorities during Rivera’s trial and said the same man bragged about Tibbetts’ kidnapping and murder. One witness said the man said he and another person decided to dump her body “near a Hispanic male in order to make it appear that the Hispanic male committed the crime” because of the “publicity” surrounding her disappearance.

But defense attorneys say they were only told about one witness after they rested their case, the other after the verdict.

They say the witness information could bolster their defense. But prosecutors say there are differences between Rivera’s testimony and the new accounts, and they disagree that her abduction could be part of a trafficking ring.

“There’s no evidence that we’re aware of, you know, that a sex trafficking house exists in Poweshiek County,” Mitch Mortvedt told CBS News’ Meg Oliver. Mortvedt oversaw Tibbetts’ case for the Iowa Department of Criminal Investigation. He said he remains confident in the investigation and conviction.

“The evidence that was discovered, you know her blood was in his trunk of his vehicle. And again, the statements that he gave that all came out during trial that’s where our confidence lies,” Mortvedt said.

The defense noted blood tests from Rivera’s trunk showed DNA from people other than Tibbetts. They are also requesting information from prosecutors on sex trafficking investigations in the region. The judge said he expects to have a decision regarding the potential evidence by the ‘week’s end. CBS News reached out to the Tibbetts family for their reaction, but they’re declining to comment at this time