Modern hostage negotiation principles were established in 1972 when
New York City Police Department detective
Harvey Schlossberg, also a psychologist, recognized the need for trained personnel in crisis intervention. Schlossberg had worked on the
David Berkowitz ("Son of Sam") case, and had instituted other psychological principles in police work, including
psychological screening of police applicants. Schlossberg's negotiation strategies were used during the
1973 Brooklyn hostage crisis and were crucial in ensuring the peaceful resolution of the standoff. The first hostage negotiators were often deployed as elements of
police tactical units and merely created a diversion while they deployed. In modern usage, while sometimes acting independently, hostage negotiation teams are often deployed in conjunction with police tactical units, with the tactical teams only sent in should negotiations fail. The
Federal Bureau of Investigation Crisis Negotiation Unit (which developed the Behavioral Change Stairway Model) and
Singapore Police Force Crisis Negotiation Unit are examples of specialized units trained in these techniques. ==Behavioral Change Stairway Model==