Final answer:
Law enforcement officers need a reasonable suspicion based on observable facts to detain and frisk someone for gun possession.
Step-by-step explanation:
The level of knowledge of gun possession needed for law enforcement officers to detain and frisk an individual is based on the principles established in the landmark case Terry v. Ohio. According to the Supreme Court decision, police officers can stop a person if they have a reasonable suspicion that the person has committed or is about to commit a crime. Likewise, they may frisk the individual if they have a reasonable suspicion that the person is armed and dangerous.
This means that officers must have specific and articulable facts that support their belief that the individual is involved in criminal activity and has a weapon. The suspicion cannot be based on a hunch or a general profile. It should be based on objective criteria observed by the officer, such as a bulge in the clothing that suggests the presence of a weapon.
Overall, the level of knowledge required for law enforcement officers to detain and frisk someone for gun possession is a reasonable suspicion based on observable facts that support the belief that the person is armed and dangerous.