Just at death the body temperature was 98 degrees Fahrenheit (approx Normal body temperature)

It was 87 degree at 11:55

and 75 degree at 12:45

Consider y=Ce^(kt)+Ts

Ts = 75 degree

let be time of death. temp 98

be 11:55 temp 87

be 12:45 temp 80

So

i.e.

----------eq1

----------eq2

----------eq3

Now do eq3 -eq2 and eq2 -eq1 and use t_3 -t_2 = 50 minutes

So a bit calculation will give you

( is in minutes here)

Find and you can take the guess of murderer on basis of