I'll put this as delicately as I possibly can. Apologies if anyone is offended.
That when a person dies in the lateral position,and if they're moved on their side,air escapes from within their mouth which gives the impression,to some,that they're still alive. It sounds almost like a gasp for breath,and unless you've had previous experience of this happening,a person who doesn't realise what's happening could possibly try and bring them back to life,as it can sound like choking.
I still have to wonder if this happened with Sheila,as in the last throes of dying,that choking could be heard,and that one of the officers put her on her side thinking that she could be saved.?
If this had been the case,then Sheila couldn't have been dead for very long,as this doesn't occur if it's hours later,only within an hour or two of death. The way to tell how long a person has died in this case,is by the amount of blood,a small amount indicates that they haven't been dead for long,as in death,the heart stops pumping anyway. If there was obviously a large amount of blood,then they'd been dead longer allowing for leakage from wounds as opposed to blood having been pumped out.