"The classical method of estimating time of death is the rate method, which measures postmortem (after death) stages and the types of transformation a body undergoes such as cooling rates (algor mortis), stiffening (rigor mortis ), initiation and duration, postmortem lividity (discoloration stains), degree of putrefaction, adipocere (body fat saponification), and maceration (tissue softening due to the presence of liquid)."

The Westernhoffer-Rocha-Valverde method was first applied in forensic medicine by the Brazilian forensic pathologists Martinho da Rocha and Belmiro Valverde.  The Wesernhoffer-Rocha-Valcerde method refers to the observation of blood crystal within the human body after death. As the blood undergoes putrifaction, crystal blades appear in several forms (i.e. clustered patterns, crisscross, and colorless).  The crystals appear after about three days and can last as long as 35 day.