In the early 1970s, two police sergeants from the Los Angeles Police Department, in consultation with medical personnel and other experts, discovered that most of the drugs which impair a person's ability to safely operate a motor vehicle could be separated into seven distinct categories, each with distinctive effects on the body: (1) central nervous system depressants; (2) central nervous system stimulants; (3) hallucinogens; (4) phencyclidine; (5) narcotic analgesics; (6) inhalants; and (7) cannabis. The officers developed a Symptomatology Chart that could identify and explain in court which drug or drugs were impairing a person at the time of contact with the police. The Drug Recognition Expert program does work and has a proven track record in the United States since the early 1980s. It does, however, require the support of the law enforcement community and the criminal justice system as a whole to make it as effective in Canada.