Police Self Defense training is very specific. Police officers have to learn self defense for both armed and unarmed situations. They need to use a martial art that can subdue a criminal suspect without harming them. Grappling arts are essential as they can control the suspect without striking them.

Martial art, combat sport, and a self defense system that focuses on grappling and especially ground fighting. Brazilian (Gracie) Jiu-Jitsu is used by law enforcement in the USA, Canada, Brazil and many other countries in the world.

In Sao Paulo, Brazil, the police has formed an unarmed police unit with offers trained in Jiu-Jitsu.
This special police unit is called the “Tropa do Braço” ( Troop of Arms). They consist of 140 officers who have trained for a minimum amount of 3 months. Some officers are black belts while some are still beginners.
The Brazilian police took inspiration from the French police who dealt with violent protests in Paris in 2005, in the same way.
“We want to use less aggressive resources,” Emerson Massera, a military police captain, told Ultimo Segundo. “We hope that physical force alone contains the most agitated protesters.”
This is not the only police or military unit in Brazil that trains BJJ. Brazil’s famous BOPE has many BJJ black belts in their ranks.

• Advantages: BJJ is specialized in ground fighting and in joint locks and chokes. It is perfect for controlling a much larger opponent. The Gracie Jiu-Jitsu version is more suitable than the sport Jiu-Jitsu version as it is more focused on self defense instead of sport specific techniques. BJJ training and rolls are done against a fully resisting opponent so you know what techniques are really efficient.
• Disadvantages: With rise of sport BJJ, it is hard to find qualified instructors that know the self defense aspect of Brazilian Jiu-Jitsu.

Mike The Cop is a popular yt channel that deals with police methods and viral events. He recently published a clip named Fatal Shooting of Firefighter: Why Every Cop Should Train BJJ – here he details an incident where a firefighter lost his life in  a tragic circumstance:

Bruno Malfacine Is The Greatest BJJ Competitor Ever To Step On The Mat & For The First Time Ever – The Only 10x Weight Class Black Belt World Champion In History – Wants To Show You How He Wrecks The Big Guys .