Answer and explanation:
I believe the description "courtroom lynchings" means the trials were not fair. The police were able to prevent people from actually lynching - beating to death with their own hands - black people who they believed had committed a crime. However, the trial was not a fair one; it was done with the purpose of condemning so that the crowds would be pleased. Racism prevailed instead of justice.
Tom Robinson's trial is a fictional one, in the plot of the book "To Kill a Mockingbird". But the Scottsboro Boys' trials were real and extremely unjust. A group of black teenagers was accused of attacking and raping a group of white boys. They were quickly sentenced to death, some being able to escape it through several appeals in the judiciary system, other having to truly run for their lives. Their case is now a big example of racism and injustice. They were indeed courtroom lynched, being judged without an opportunity to properly defend themselves.