When may evidence given by a person be deemed inadmissible ?

Evidence that can not be presented to the jury or decision maker for any of a variety of reasons: it was improperly obtained, it is prejudicial (the prejudicial value outweighs the probative value), it is hearsay, it is not relevant to the case, etc.

The Tuskegee Airmen helped pave the way in the Civil Rights Movement by demonstrating that African Americans were capable of fighting and flying planes in the same courageous manner as whites, and that they deserved to be treated equally. They also aided in the eventual integration of the United States' armed forces.

I hope I helped! ^-^