hostage negotiator

Etymology
Modern hostage negotiation principles began in 1972 when, then New York Police Detective Harvey Schlossberg, a police officer with a PHD in psychology, recognized the need for trained personnel in the intervention of hostage situations.

Noun

 * 1)  A person who negotiates with a person, or groups of persons, for the release of a person, or groups of persons.

Usage notes
Hostage negotiation has developed into a science. Hostage negotiation teams are often deployed in conjunction with SWAT teams or sometimes independently.

Translations

 * Hungarian: túsztárgyaló