Difference between respired and unrespired lungs (Live birth vs Dead Birth)

The knowledge whether a dead fetus was a still birth or died after coming into the environment (Live Birth) is very important in Forensic Science. This is important specially in countries where killing of neonate in the name of black magic is prevalent. Similarly, killing of female fetus/ newborn is also common in some part of the world. Killing a newborn is Crime in most part of the world and differentiation between the two can be made based upon the study of the lungs in the postmortem. 

Postmortem finding of a respired and unrespired lungs have many differences. The unrespired lungs is parenchymatous like a liver occupying lesser volume. Being condensed and no air particle inside it tends to sink in the water with density higher than that of water. 

Respired lungs on the other hand have spongy elastic appearance with lesser density and hence floats in water. It is expanded covering the heart and with respiration the cardiac circulation changes and the patency of the vessels is maintained making it ooze with frothy blood when cut into pieces.

The following are the characters based upon which the differentiation can be made between the two.

Character	Unrespired Lungs	Respired Lungs
Weight in relation to body weight	1/70	1/35
Volume	Small	Large and covers the heart
Consistency	Liver Like: Dense firm non crepitant	Soft, spongy, elastic, Crepitant
Extension	Up to the level of 4th and 5th rib	Up to the level of 6th and 7th rib
Specific gravity	1.04	0.94
Margin	Sharp	Rounded
Color	Uniform reddish	Mottled/ marbled appearance
Air vesicle	Not inflated	Inflated
Section	Little froth less blood exudates on pressure	Abundant frothy blood exudates
Breslow life test	Whole or part sinks	Expanded
Microscopy	Cuboidal lining	Squamous Epithelium
Blood vessel	Less patent	More Patent

Difference between Rigor Mortis and Cadaveric Spasm

Though rigor mortis and cadaveric spasm both occur both following death but they are totally different things. Cadaveric spasm is a localized contraction of muscle that was occurring during the time of death and perisisted then after unlike Rigor mortis which developed through out the body including visceral muscle. There is a period of flaccidity before rigor mortis  develops. The following points helps us differentiate between the cadaveric spam and rigor mortis.

Know the physiology behind rigor mortis 

Character	Rigor Mortis	Cadaveric Spasm
Time Of Onset	Within 1-2 hours of death	At the time of Death
Occurrence	Occurs in all death except burn	Predisposed by sudden violent death
Muscle	Both Voluntary and involuntary Muscle Heart is the first to be involved Small muscle of digits develop it last	Local Voluntary Muscle eg. Hand with knife in suicide
Muscle Stiffening	Moderate force required to break it	Great Force required to break
Primary flaccidity	Occurs	Does not occur
Mechanism of Production	Known	Still Obscure
Response of Electrical Stimuli	Absent	Present
Medico Legal Importance	Gives idea about Time since death	Gives idea about Mode of Death