Post mortem lividity or hypostasis is the settling of blood under the influence of gravity which develops in the early post mortem interval. Lividity generally becomes apparent within a short period after death and is said to Become fixed between 8 and 12 hours after death. Described tests for fixation of lividity include absence of skin blanching after thumb pressure and lack of shifting of lividity after rolling over the body. We examined 12 bodies where the time of death and position of the body were known. At regular intervals after death, the thumb pressure test and the body rotation test were performed. At periods of up to 24 hours after death lividity had not fixed using either test. We conclude that determination of the post mortem interval based on fixation of lividity is unreliable. Furthermore, conclusions relating to movement of the body after death should not be based entirely on the presence of paradoxical lividity. Post mortem lividity or hypostasis is the settling of blood under the influence of gravity which develops in the early post mortem interval. Lividity generally becomes apparent within a short period after death and is said to Become fixed between 8 and 12 hours after death. Described tests for fixation of lividity include absence of skin blanching after thumb pressure and lack of shifting of lividity after rolling over the body. We examined 12 bodies where the time of death and position of the body were known. At regular intervals after death, the thumb pressure test and the body rotation test were performed. At periods of up to 24 hours after death lividity had not fixed using either test. We conclude that determination of the post mortem interval based on fixation of lividity is unreliable. Furthermore, conclusions relating to movement of the body after death should not be based entirely on the presence of paradoxical lividity.