3 Progression of Rigor Mortis Time After DeathEventAppearanceCircumstances2 – 6 hoursRigor beginsBody becomes stiff and stiffness moves down bodyStiffness begins with the eyelids and jaw muscles after about 2 hours, then center of the body stiffens, then arms and legs12 hoursRigor completePeak rigor is exhibitedEntire body is rigid15 – 36 hoursSlow loss of rigorLoss of rigor in small muscles first, followed by larger musclesRigor lost first in head and neck, and last in bigger leg muscles36 – 48 hoursRigor totally disappearsMuscles become relaxedMany variables can extend rigor beyond the normal 36 hours
4 Factors Affecting Rigor Mortis EventEffectCircumstancesTemperatureCold temperatureInhibits rigorSlower onset and slower progression of rigorWarm temperatureAccelerates rigorFaster onset and faster progression of rigorActivity before deathAerobic exerciseLack of oxygen to muscles, the build up of lactic acid, and higher body temperature accelerates rigorSleepSlows rigorMuscles fully oxygenated will exhibit rigor more slowlyBody weightObeseFat stores oxygenThinBody loses oxygen quickly and body heats faster
5 What Happens During Decomposition Stages of DecompositionStageWhat Happens During DecompositionInitial decayCorpse appears normal on the outside, but is starting to decompose from the actions of bacteria and autolysis.PutrefactionOdor of decaying flesh is present and the corpse appears swollen.Black putrefactionVery strong odor. Parts of the flesh appear black. Gases escape and the corpse collapses.Butyric putrefactionCorpse is beginning to dry out. Most of the flesh is gone.Dry decayCorpse is almost dry. Further decay is very slow from lack of moisture.
6 Third-stage larva has three slits (4-5 days old) First stage larvaSecond stage larvaThird stage larva
7 Blowfly Life Cycle Stage Size (mm) Color When First Appears Duration in PhaseCharacteristicsEgg2WhiteSoon after death8 hoursFound in warm, moist areas of the body like the eyes and mouthLarva 151.8 days20 hoursBlack mouth hooks visible; thin body; 1 spiracle slit near anusLarva 2102.5 days15-20 hoursBlack mouth hooks; actively feeding; 2 spiracle slitsLarva 3174.5 days36-56 hoursBlack mouth hooks; fat body; 3 spiracle slits
8 Blowfly Life Cycle, Continued StageSize (mm)ColorWhen First AppearsDuration in PhaseCharacteristicsPre-pupa9Light brown8-12 dayshoursLarva migrates away from the body and to a dry areaEarly and late pupaLight brown; changes to dark brown18-24 days6-12 daysImmobile; does not feed; changes to dark brown with age; pupa case splits open prior to adult emergingAdultVariesBlack or green21-24 daysSeveral weeksIncapable of flight for the first few hours