What can the FBI investigate?

Ford has been very careful to not remember anything that would allow Kavanaugh to show that he wasn't at the alleged party. Every witness she cited has stated, under oath, that what she described didn't happen.

So what will the FBI investigate? Are they going to go house to house and ask the current residents if there was a party at the house when the parents were gone 36 years ago?  They can ask the people who have already sworn under oath if they are going to admit to perjury. But other than that there's really nothing they can investigate.

Ramirez is on record as being unsure of her claim and refusing to speak under oath. The FBI can't compel her to talk. Further as with Ford the people she cites as witnesses have all said that her story is incorrect.

Swetnick is clearly a loon but if she tells her story under oath she'll be liable for both civil and criminal prosecution for aiding and abetting gang rapes.  Given that she too has failed to provide any corroborating details, that her age is inconsistent with her story, and that her story has a multitude of internal contradictions she could never be a credible witness.

The very fact that all the Democrat accusers, and they're all hard core Democrats, have had to be very very light on details to avoid the chance that Kavanaugh could say something like "I couldn't have been there me and my family were on vacation that weekend" means that there is nothing for the FBI to investigate.

If a woman went to the FBI and said she'd been raped but she couldn't remember where or when but she was sure it was Obama we know the FBI would politely refer her to her local police not treat her claim seriously.