Definition - What does Smoking Gun mean?
Smoking gun is an informal term that is used to describe a piece of evidence that proves beyond any doubt that a certain person or group committed a specific crime.
"Smoking gun" is a reference to a murder weapon, which belongs to the killer, being discovered after a murder has taken place.
Justipedia explains Smoking Gun
Even if a "smoking gun" piece of evidence is discovered, a trial still needs to take place. The defendant still must be formally declared "guilty" by the jury before they are sentenced to a punishment for the crime.
An example of a smoking gun piece of evidence could be if a burglar dropped a ring that they were wearing in the home where they broke in, and the ring had their name and DNA on it.