Hijacker Invention

This invention could be used in planes.
The seat of each traveller is eqquipped with alie detector.
Before the plane takes off every passenger is asked some questions about his or her intention to fly in that plane.
If the detector finds out that the person is lying when the question about hijacking the plane is asked, the injector underneath the seat gets activated and injects a sleeping serum into the passenger's leg.
In the case that the passenger would answer the question about hijacking with "yes", the injection would be injected in the leg as well.
While the alarm bells are ringing the presumed hijacker can be easily imprisoned by the police.

By Alexandra Zinner