Trump appears to be referring to Special Counsel Robert Hur's recent report into Biden's handling of classified documents.
Hur's report did not say that Biden was "incompetent to go to court." A similar claim,
made by Georgia Republican Representative Marjorie Taylor Greene, was recently debunked by Newsweek.
Hur's assessment included judgments about Biden's ability to recall events in his life, where he stored classified documents, and whom he shared sensitive information with.
Hur said any trial would take years to bring to court and, in that situation, Biden "would likely present himself to a jury, as he did during our interview of him, as a sympathetic, well-meaning, elderly man with a poor memory."
He added: "It would be difficult to convince a jury they should convict him—by then a former president who will be at least well into his eighties—of a serious felony that requires a mental state of willfulness."
Also, the report does not state that Biden was "incompetent to go to court" as Trump claims.
Hur argued that if, hypothetically, Biden were to stand trial over his handling of confidential documents, it would require a "mental state of willfulness", a challenge that would be more demanding by Biden's age at that point.
While Hur stated Biden was an "elderly man with a poor memory", this is distinct from mental competency to stand trial, which is assessed by psychiatric evaluation.