I was looking at this today, due to the prosecution claims in the Chrisopher Coleman case.
Googling, I found this page: http://www.pathguy.com/TimeDead.htm
and then this online calculator: http://www.swisswuff.ch/calculators/todeszeit.php
I left the “Henssge empiric correction factor” at the default value of 1.
I believe the day was cool (using a weather site), the ambient temperature might have been around 55F = 12.7C
The temperature at 11am was 90.4F = 32.4C ( this should be rectal ).
I guessed the body weight as 70kg.
Using these figures, the calculator says:
“Estimated time of death: 6h 30min (95% tolerance: 3h 30min to 9h 30min); rounded to 30min.”
So based on the temperature, it appears there is in fact no reason to disbelieve Coleman’s testimony that his family was alive when he left the house at 5:43 a.m.