BBC News, Washington
The recent killing of an unarmed Virginia doctor has raised concerns about what some say is an explosion in the use of military-style police Swat teams in the United States.
Armed with assault rifles, stun grenades - even armoured personnel carriers - units once used only in highly volatile situations are increasingly being deployed on more routine police missions.
Professor Peter Kraska, an expert on police militarisation from Eastern Kentucky University, says that in the 1980s there were about 3,000 Swat team deployments annually across the US, but says now there are at least 40,000 per year.
"I have no problem with using these paramilitary style squads to go after known violent, armed criminals, but it is an extreme tactic to use against other sorts of suspects," he said.
Dr Kraska believes there has been an explosion of units in smaller towns and cities, where training and operational standards may not be as high as large cities - a growth he attributes to "the hysteria" of the country's war on drugs.