Deborah Ramirez's sworn statement to the FBI is corroboration of Dr. Ford's sworn testimony.
in the law of criminal evidence "similar fact" evidence is used as direct corroboration. Similar fact evidence being admitted at trial is highly restricted because it can be both highly probative and prejudicial.
"In the law of evidence, similar fact evidence (or the similar fact principle) establishes the conditions under which factual evidence of past misconduct of accused (Ramirez accusation) can be admitted at trial for the purpose of inferring that the accused (Kavanaugh) committed the misconduct at issue (Dr. Ford accusation)."
https://www.cbsnews.com/news/brett-kavanaugh-accuser-deborah-ramirez-interviewed-by-fbi-as-part-of-assault-probe/
If the Republicans want to pretend the FBI background check was a thorough and complete criminal investigation then the Ramirez similar fact evidence principle blows a huge hole in their campaign of "no corroboration" of a crime against Dr. Ford by Kavanaugh, using even this standard.
https://en.m.wikipedia.org/wiki/Similar_fact_evidence
(edited)
In Canada, the rule is established in R. v. Handy, 164 CCC (3d) 481, 2 SCR 908 (2002):
Evidence of prior bad acts by the accused will be admissible if the prosecution satisfies the judge on a balance of probabilities that, in the context of the particular case, the probative value of the evidence in relation to a specific issue outweighs its potential prejudice and thereby justifies its reception.
Questions may arise as to how the Court will measure the elements of this rule:
i) What constitutes a prior act of misconduct?
(Any past misdeed does not have to proven as a conviction criminal conviction)
ii) Why does the Court speak of evidence in relation to a 'specific issue'? Specific issue is almost always identification where a similar fact application is brought by the prosecution.
Good measure of probity need for similar fact evidence, and what other issue beyond disposition or propensity evidence?
iii) How is probative value determined?
Nature of similarity between details, distinctive features and circumstances of past act and current offence
Proximity in time between past act and current offence
Number of occurrences of the similar acts
Any intervening event
Any other factor tending to support or rebut the unity of past act and conduct in question (i.e. appearance of collusion)