In March 2015 the IPCC Learning the Lessons Bulletin No. 23 is solely around custody.
It reviews several case studies, some which resulted in deaths and others that didn’t. The case studies cover many areas including Section 136 detainees, head injuries, intoxication levels, rousing detainees, and drunk and incapable to name a few.
Following each case study is a ‘key questions’ section, and the over-arching question being – ‘Could it happen here?’
Link is attached and well worth a read.