of 20 /20

Rigor Mortis

Embed Size (px)

Text of Rigor Mortis

Page 1: Rigor Mortis



Page 2: Rigor Mortis


• Somatic death• Contact flattening• Muscle irritability &response to mech/elect

stimuli persists• Peristalsis ,ciliary movements, WBC movements

may be present • Focal twitching +nt-dying neurons• Loss of sphineter tone• Muscle protoplasm slightly alkaline

Page 3: Rigor Mortis


• Rigor mortis is the stiffening of muscles after death.• In forensic pathological practice, the intensity of

rigor mortis is assessed on a pure subjective basis, meaning whether skeletal muscles offer resistance when joints are moved (flexion/extension).

• Post-mortem rigidity is characterized by a loss of muscle elasticity and plasticity, an increase in stiffness, and shortening of muscle length.

Page 4: Rigor Mortis

Phases of rigor mortis

1st phase -delay period2nd phase -onset phase(reversible)3rd phase-rigor(irreversible)4th phase -resolution

Page 5: Rigor Mortis

MECHANISM OF RIGOR MORTIS• It is a physico-chemical change in muscles due to lack of oxygen• Muscles are composed of myofibrils, which are again composed of myofilaments.• Two types of myofilaments : actin and myosin• Under the influence of adenosine triphosphate (ATP), actin and myosin form a contractile

compound, actomyosin.• With decrease of ATP levels post-mortem(85%), actin and myosin enter into a nonshiftable

and rigid state of adhesion until, under the influence of autolysis and putrefaction, protein disintegration of the myofibrils leads to loosening of rigor mortis (secondary relaxation)

• Maximum rigidity at ATP levels of 15%• Lactic acid -.3%• Sources of ATP-1)Phosphagen system 2)glycogen-lactic acid system 3)aerobic system • Onset of rigor mortis is earlier and more rapidly progressing in red muscles than in white

muscles, which has been attributed to ATP levels falling more rapidly after death in red muscles than in white muscles

Page 6: Rigor Mortis


• Shapiro-Rigor mortis develops in all muscles at the same time and at the same speed. However, because of the different diameters of the muscles involved, post-mortem rigidity becomes noticeable at first in smaller muscle groups

• Nysten’s rule-descends from the head to the shoulder girdle and arms and then to the legs, greater diameter of the muscle groups located at joints that are located farther downwards the body and disappears in the same order in which it has appeared

Page 7: Rigor Mortis

Time of onset and duration

Time of onset• India

begins 1-2hrs after death further 1-2hrs to develop• Temperate countries begins 3-6hrs after death further 2-3hrs to develop

Duration• India winter-lasts 24-48hrs summer-lasts18-36hrs• Temperate regions 2-3days

Page 8: Rigor Mortis

Testing of rigor mortis

-lifting of eyelids-depressing jaw-bending of neck and joints

Page 9: Rigor Mortis

Post mortem changes

• Heart -Myocardial hypertrophy -ante mortem dilatation/myocardial deg -systolic/diastolic stoppage • Skin –cutis anserina/goose skin• Testes drawn up• Seminal ejections• Expelling of fetus from uterus

Page 10: Rigor Mortis
Page 11: Rigor Mortis


Page 12: Rigor Mortis

Factors affecting rigor mortis

Early onset• Cholera, typhoid, TB, cancer• firearms, electro, lightning• cutthroat• Strychnine poisoning• OP poisoning• CO poisoning –delays

disappearance• Cold weather• Children and old people

Late onset• Asphyxia• Sev hemorrhage• Apoplexy• Pneumonia• Nervous disease• Normal saline perfusion• Resting and healthy


Page 13: Rigor Mortis

Early disappearance• Strychnine poisoning• Bact inf –gas gangrene• Children and old people

Late disappearance• CO poisoning• Healthy and resting

muscles• Cold weather

Page 14: Rigor Mortis

Absent rigor mortis • Fetus of less than 7 months of age• Septicemia • Advanced states of multiple sclerosis,

amyotrophic lateral sclerosis, or Duchenne muscular atrophy

Page 15: Rigor Mortis

Medico legal importance• Helpful in determining whether a body has been moved after death. If a body is found in

an illogical posture, this means a body position that would not have been maintained under the influence of gravity (primary relaxation of the muscles after death), this position implies that the body has been moved after the development of rigor mortis

• Examination of the palms and the inside aspects of the fingers becomes difficult so that current marks or defence injuries located here may be overlooked

• In infants and children, a marked dilation of the anal orificium may be observed post-mortem . As mentioned before, immediately as death occurs and preceding the onset of rigor mortis, the whole body musculature loses its tone. In children a dilated anal orificium (because of the loss of tone of the musculature immediately as death occurs) may be fixed by rigor mortis, and this finding may even persist after rigor mortis has faded. Therefore, anal dilation alone is not a sufficient marker for penetrative anal abuse of children prior to death

• Muscle relaxation immediately after death with opening of the eyes and the mouth with subsequent fixation in rigor mortis may give the face a somehow grimace-like look post-mortem. However, one cannot predict from the face of a deceased, as often assumed by the unaware, whether this individual’s last moments were of fear or fright

Page 16: Rigor Mortis


1. Heat stiffening2. Cold stiffening3. Cadaveric spasm

Page 17: Rigor Mortis

Heat stiffening

• >650 C• More marked than that found in rigor mortis• Depends on intensity and duration for which

applied• Burning ,high voltage electric shock, fall into hot

liquid• Mechanism- denaturation and coagulation of

muscle protein• Cooked meat appearance

Page 18: Rigor Mortis

Cold stiffening

• Due to freezing of body fluids and solidification of subcutaneous fat

• When forcefully flexed-ice cracking in synovial fluid

• If again placed in warm temp-rigor appears rapidly and passes off quickly

• Medicolegal importance-subcut fat hardening in infants simulates ligature mark

Page 19: Rigor Mortis

Cadaveric spasm/Instantaneous rigor

• Complete rigor mortis occuring at the moment of deathand involving a hand ,limbor even an entire body

• No stage of primary relaxation

• Single group of voluntary muscle

Page 20: Rigor Mortis

Causes ,mechanism and MLI

• Suddendeath• Excitement• Fear • Severe pain• Exhaustion• Cerebral haemorrhage• Firearm wounds of head• Convulsant poisons

• Mechanism – 1.Neurogenic, 2.Adrenocortical exhaustion

• Medicolegal importance-

1.Weapon2. Material evidence 3.Antemortem drowning