Best practices – For the purpose of this chapter, best practices are defined as methods, techniques, and procedures that have consistently shown by research and experience to produce superior results and are established or proposed as a standard, suitable for widespread adoption in the law enforcement profession.

Completed investigation - The final work product of the IIT for the purpose of informing the prosecuting attorney's charging decision. An independent investigation must be completed to inform any determination of whether the use of deadly force met the good faith standard established in RCW 9A.16.040 and satisfied other applicable laws and policies.

Deadly force – As set forth in RCW 9A.16.010, "deadly force" means the intentional application of force through the use of firearms or any other means reasonably likely to cause death or serious physical injury.

Evanescent evidence – Physical evidence that may be degraded or tainted by human or environmental factors if left unprotected or unpreserved for the arrival of the independent investigative team (IIT); identification and contact information for witnesses to the incident; photographs and other methods of documenting the location of physical evidence and location/perspective of witnesses.

Good faith standard – As set forth in RCW 9A.16.040, ""good faith" is an objective standard which shall consider all the facts, circumstances, and information known to the officer at the time to determine whether a similarly situated reasonable officer would have believed that the use of deadly force was necessary to prevent death or serious physical harm to the officer or another individual."

Great bodily harm – As set forth in RCW 9A.04.110, "great bodily harm" means bodily injury which creates a probability of death, or which causes significant serious permanent disfigurement, or which causes a significant permanent loss or impairment of the function of any bodily part or organ.

Independent investigative team (IIT) – A team of qualified and certified peace officer investigators, civilian crime scene specialists, and at least two nonlaw enforcement community representatives who operate completely independent of any involved agency to conduct investigations of police deadly force incidents. An IIT is created when multiple law enforcement agencies enter into a written agreement to investigate police use of deadly force incidents in their geographical regions. A single law enforcement agency may fulfill the independent investigative function, provided it is not the involved agency.

Initial incident response – This is the period in time immediately following a police use of deadly force incident, and prior to the arrival of the IIT, when involved agency personnel on scene and other first responders immediately take actions to render the scene safe and provide or facilitate life-saving first aid to persons at the scene who have life threatening injuries.

Involved agency - The agency that employs or supervises the officer(s) who used deadly force. There can be more than one "involved agency."

Member agency – Each of the agencies that enters into a written agreement to investigate police use of deadly force in their geographical region.

Necessary – As set forth in RCW 9A.16.010, "necessary" means that no reasonably effective alternative to the use of force appeared to exist and that the amount of force used was reasonable to affect the lawful purpose intended.

Prosecutor's review - The period of time when the IIT presents a completed investigation to the prosecutor, who then reviews all the facts and makes a charging decision.

Substantial bodily harm – As set forth in RCW 9A.04.110, "substantial bodily harm" means bodily injury which involves a temporary but substantial disfigurement, or which causes a temporary but substantial loss or impairment of the function of any bodily part or organ, or which causes a fracture of any bodily part.