Skydiver69
Unless I'm reading your post wrong you seem to be repeating the gist of my post. I think the husband gambled on the police not attending, or only attending to deal with the aftermath of an accident along with others like the ambulance service and taking the death (if the wife had died) as an accident.
What struck me when I first heard this on the radio was the thoughts the wife must now be having. It's bad enough if a stranger attempted to kill her, but she may have sat opposite her husband for breakfast that morning and could now be thinking he didn't expect her to make it through the day.
All that of course is if he did do what he is charged with.
You probably have a lot more idea than me on how easy or hard things would be to prove in this case.