If it is true that no code was called, that's a smoking gun for sure.

I doubt the ED chart notes would have everything written in--I've witnessed omissions for less reason. The chart is a legal document, and as such should be subpoenaed if there is a real investigation into his death.

While it's true that it is possible to die while on life support (ventilator, IVF etc.), it is also very easy to kill someone on life support. The people who know how to resuscitate you also know how to kill without a trace: a precordial thump at the wrong time, saline ice cubes in the ET tube, an injection of KCl, messing with the vent settings, etc. etc. there are countless quick, easy and untraceable ways.