Definition - What does Petit Jury mean?
A petit jury is a jury chosen specifically to render a verdict after hearing evidence at trial. A petit jury is distinct from a grand jury, which considers evidence from a prosecutor to determine if probable cause exists to believe that a defendant committed a crime.
In the English common law tradition, petit juries typically consist of 12 citizens.
Justipedia explains Petit Jury
One of the ancient rights guaranteed by the English common law tradition is the right to have questions of fact, in both criminal and civil cases, decided by petit juries. Questions of fact are decided after a group of citizens listens to evidence presented by both the prosecutor and the defendant in criminal cases, or the plaintiff and respondent in civil cases.
After hearing the evidence, a petit jury deliberates or meets behind closed doors to discuss the evidence, and renders a verdict. In other words, petit juries decide "what happened" in a case.
Petit juries are also known as trial juries and common juries.