Cadaveric rigidity and cadaveric spasm


Cadaveric rigidity (Rigor mortis)

Cadaveric spasm

Production

Freezing and exposure to temperature

above 65°C will produce rigor

Cannot be produced by

any method after death

Mechanism

Known. Reduction of ATP 

Not clearly known

Predisposing

factor 

Nil

Sudden death, excitement, fear,

exhaustion, nervous tension, etc

Time of onset

1-2 hours after death

Instantaneous

Muscles involved

All the muscles of the body,

both voluntary and involuntary

Usually restricted to a

single group of voluntary muscles

Muscle stiffening 

Not marked; moderate force

can overcome it

Marked; very great force is required

to overcome it

Molecular death

Occurs

Does not occur

Body heat

Cold 

Warm

Electrical stimuli 

Muscles do not respond

Muscles respond

Muscular reaction 

Acidic

Alkaline 

Medicolegal

importance 

Indicates time of death

Indicates mode of death, i.e. suicide,

homicide or accident


Reference: 

1. The Essentials of Forensic Medicine & Toxicology, 34th edition, Dr. K.S. Narayan reddy and O.P. murty, P. No. 155 

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