Black fibers were found in the crotch of JonBenet's underwear. The fibers were sourced as coming from the black shirt John wore that night to the White's dinner party.
John told an investigator in an interview that he did not undress her before taking her upstairs that night. Patsy did. Patsy confirmed that. There is no obvious way to explain why fibers from the type of shirt John was wearing when he says he put her to bed were found in her underpants.
76.8% of people who sexually abuse children are adults:
https://americanspcc.org/child-sexual-abuse/
I can't.
If the paintbrush was never used, an autopsy could more easily reveal that prolonged prior abuse was going on and that would point directly to John. This is what they were desperately trying to cover up with the paintbrush, and this is why she was cleaned after the fact.