May 14, 2014
Impleader is where a defendant brings another party into the case and says, "If I am liable to the plaintiff, you are liable to me."
For example, let's say Patty owns a store with a smoke alarm. The smoke alarm is manufactured by Dandy Smoke Alarms. Dolittle Repair Shop is responsible for maintaining and fixing the smoke alarm.
One day there is a fire but the smoke alarm does not work. Patty sues Dandy. Dandy, the defendant, sues Dolittle in the same case, claiming that Dolittle failed to properly repair the smoke alarm. We would say Dandy impleaded Dolittle. Dandy argues that if Dandy owes Patty money, then Dolittle owes money to Dandy.
Now Patty is the plaintiff, Dandy is the defendant and third-party plaintiff, and Dolittle is a third-party defendant. All of these lawsuits can be resolved in the same case.