I was wondering this recently. It's hard to imagine this happening here in the UK. The thought of police in riot gear kicking down doors and waving guns around sounds beyond crazy to me.
About half the people killed by police have mental health problems. This is an estimate because national data isn't collected. http://www.theguardian.com/us-news/2015/apr/03/idaho-police-...
http://tacreports.org/storage/documents/2013-justifiable-hom...
But, for the UK, don't forget the several bad shootings of innocent or unarmed men. Wikipedia has a list of all killings involving a police officer in the UK. http://en.wikipedia.org/wiki/List_of_killings_by_law_enforce...
We don't shoot many people, America do. It's such a huge, cavernous gulf in magnitude that I have no idea what point you're trying to make with your last paragraph.
Also: yes, even those few deaths are totally unacceptable in the UK. People are shocked by police shootings; investigations are rigorous. Contrast that to the US where shootin a dog sparks mass outrage but shooting a drunk pregnant woman doesn't.
The classic example is if the police think that evidence could be destroyed very quickly, e.g., electronic records.
Either someone is in danger, in which case no-knock isn't needed, or they're not, in which case why the hell is a SWAT raid being carried out on the basis of an anonymous tip?
For one, you could detect these no-knocking individuals quite easily:
- Cameras on the exterior of the property
- Motion lights, motion sensors, motion bells are all quite cheap.
And re: destruction/obfuscation of electronic evidence-
-"One-click" destruction scripts, etc.
- TrueCrypt volumes, everywhere. Circuit breakers, power strips, etc. with switches. If you don't manage to destroy the volume, no aggressor will be able to access it.
- Degaussing setups for spinning disks, activated by similar mechanisms.
This stuff is pretty cheap, easily available. Anybody caught by these technically-incompetent police executing no-knock raids deserves to be caught.
Hell, if you don't have a few 6TB volumes full of random bits, labeled "Evidence," you aren't doing it right. Gotta tie up those investigative resources somehow.