The decision follows days of protests by Florida college students, who have been demanding an arrest.

George Zimmerman, 28, claims he shot 17-year-old Trayvon Martin in self defence during a confrontation in a gated community in Sanford, Florida.

According to reports, Zimmerman called police to report a suspicious person after he saw Martin while out on patrol. Zimmerman then followed Martin – against the advice of the police emergency dispatcher – resulting in his shooting Martin, who was unarmed.

The Guardian newspaper reported that prosecutors may not be able to charge Zimmerman because of changes to state law in 2005. Under the old law, people could use deadly force in self-defence only if they had tried to run away or otherwise avoid danger.

But under the new law, there is no duty to retreat. The change, therefore, gives a Floridian the right “to stand his or her ground and meet force with force, including deadly force,” if he feels threatened.

Around half of US states have similar laws. In essence, if a person shoots another person and there are no witnesses, then the shooter can claim to have believed they were under attack and there is little ground for prosecution.

Picture: Getty