A 68-year-old woman is discovered dead in her home in Mumbai. The body is brought to the mortuary 12 hours after discovery. On initial examination, rigor mortis is fully established in all muscle groups and beginning to disappear from the face and jaw. The skin shows early discoloration and a faint putrid odour is noted. The ambient temperature has been 32°C throughout. What is the most appropriate next step in determining the cause and time of death?