Livor mortis or lividity is the gravitational pooling of blood in the dependent parts of the body, both externally in the skin capillaries and venules but also in the internal organs. … Lividity may not be seen in bodies that are very anemic at death.
Since livor mortis can be cleared with pressure, objects pressing against the skin when livor forms can cause a pattern. This individual was lying on an “egg crate” foam mattress when he died. The foam tips of the mattress touched the skin and cleared the livor, while the cups of the mattress allowed the livor form.