A federal judge refused Friday to dismiss charges against actress Lori Loughlin, her fashion designer husband, Mossimo Giannulli, and other prominent parents accused of cheating the college admissions process, siding with prosecutors who denied that investigators had fabricated evidence.

U.S. District Judge Nathaniel Gorton rejected a bid by the defense to throw out the indictment over allegations of misconduct by FBI agents in the case that has rocked the world of higher education.

Loughlin and Giannulli are scheduled to go on trial in October on charges that they paid $500,000 to get their daughters into the University of Southern California as crew recruits even though neither girl was a rower. They denied paying bribes and said they believed their payments were legitimate donations.

An email seeking comment on the judge's ruling was sent to a lawyer for the couple on Friday.

They were among 50 people charged last year in the case dubbed "Operation Varsity Blues." Authorities said wealthy parents paid huge sums to secure their admissions at elite schools as fake athletic recruits or have someone cheat on their entrance exams.

The judge's decision came after he ordered prosecutors to explain iPhone notes written by the admitted mastermind of the admissions cheating scheme -- Rick Singer -- when he was secretly working with the government in October 2018.

In his notes, Singer wrote that investigators told him to lie to get parents to make incriminating statements over recorded phone calls. The agents instructed him to say he told the parents the payments were bribes, instead of donations, according to the notes made public in legal filings.

"They continue to ask me to tell a fib and not restate what I told my clients as to where there money was going -- to the program not the coach and that it was a donation and they want it to be a payment," Singer wrote, according to court documents.

Gorton had called Singer's claims in his notes "serious and disturbing."

The defense argued the notes show that agents bullied Singer into fabricating evidence by tricking the parents into falsely agreeing that the payments were bribes.

The agents in the case denied pressuring Singer to lie and said they had been instructing him to be more explicit with new clients who had not already gone through with the bribery scheme. Prosecutors said Singer took the notes when he hadn't yet fully accepted responsibility for his crimes. Furthermore, prosecutors said it doesn't matter whether Singer called the payments bribes or donations, because it was still an illegal quid pro quo.

Singer pleaded guilty and was expected to be a crucial witness at the trials. He began cooperating with investigators in September 2018 and secretly recorded his phone calls with parents to build the case against them.

Nearly two dozen parents have already pleaded guilty in the case, including "Desperate Housewives" actress Felicity Huffman. She served nearly two weeks in prison after she admitted to paying $15,000 to have someone correct her daughter's entrance exam answers.