He said it in his opening testimony and wrote it into his report. He got confused during his recent testimony but came back and corrected that testimony. And the Dems lose once again.

Daily Caller:    California Rep. Ted Lieu said Thursday he believes that “somebody got to” Robert Mueller to force the former special counsel to correct his testimony about his obstruction investigation of President Donald Trump.
Lieu, a Democrat, offered up the unfounded conspiracy theory in an interview on CNN when asked about an exchange he had Wednesday with Mueller during a House Judiciary Committee hearing.

During their exchange, Mueller gave would-be bombshell testimony that the reason he did not indict Trump for obstructing the Russia probe was because of a Justice Department office of legal counsel opinion that prohibits indicting sitting presidents.

“The reason again that you did not indict Donald Trump is because of [Office of Legal Counsel] opinion stating that you cannot indict a sitting president, correct?” Lieu asked Mueller in the hearing.
“That is correct,” Mueller said.
But before Democrats could celebrate too much, Mueller corrected his testimony when he appeared hours later before the House Intelligence Committee for a second round of testimony about his Russia investigation.

“Now before we go to questions, I want to add one correction to my testimony this morning,” Mueller began in his opening remarks.
“I want to go back to one thing that was said this morning by Mr. Lieu, who said, and I quote, ‘you didn’t charge the president because of the OLC opinion.'”
“That is not the correct way to say it,” he said, adding, “as we say in the report, and as I said in the opening, we did not reach a determination as to whether the president committed a crime.”