Sure:
—Defense contractors (that he will name in private session) will have alien craft artifacts or they will not.
—The IG will be able to show the alleged misappropriation of federal funds to cover the ongoing costs to reverse engineer/store/hide/coverup alien craft or they will not.
—Other whistleblowers will come forward to testify to the Committee or they will not....
and those are just a few examples—we are talking double digits of verifiable/falsifiable stuff here.
Did he claim that the were alien craft artifacts, or that someone told him there were? If it turns out there aren’t, he can still claim someone told him there were.