day in court, have one's
Have an opportunity to be heard, as in By asking Rob for an explanation the professor showed he was willing to let him have his day in court. This expression transfers the idea of a hearing in a court of law to more general use.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.