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Medicolegal Study of Rigor Mortis to Estimate Postmortem Interval

Dr. J.S. Dalal*, Dr. H.R. Tejpal**, Dr. Ashok Chanana***, Dr. Navpreet Kaur*****Professor and Head,**Addi tional Professor ,***Associate Professor ,****Junior Resident*Department of Forensic Medicine, Govt. Medical College, Amritsar.

Abstract

Rigor Mortis is an important indicator of post-mortem interval. Though it is a reliable tool of estimating postmorteminterval, it is influenced by many endogenous and exogenous factors. Temperature and humidity are veryimportant factors, their relation with rigor mortis is Observed In The Present Study.Key Words: Rigor mortis, Post mortem interval.

Introduction:Estimation of time since death is an achilles heel inforensic medicine due to great individual variabilityof the postmortem changes as a consequence ofmany influencing factors. Rigor mortis is one suchcriterion which is being widely used to determinepostmortem interval. A uniform time of appearanceand disappearance of rigor mortis cannot be madeapplicable throughout a vast country like India wheredifferent weather conditions exist throughout itsvarious parts at a given time. The present study wasdone to study the modifying effect of temperatureand humidity on the development and extent of rigor

mortis.Material And Methods:500 medicolegal autopsies were selected where theexact time of death was known and the body hadbeen kept at prevailing room temperature. Toobserve the effect of atmospheric and seasonalconditions, the period of study was divided into fourgroups corresponding to the four seasons. A goodquality digital hygrometer was used to note the dailyreadings of temperature and humidity. Presence orabsence of rigor mortis and its extent was noticed inboth voluntary and involuntary muscles. In the joints,appearance and disappearance of rigor mortis was

noted by seeing their movements for resistanceoffered.

Observations:In the present study 78.4% cases studied weremales and 21.6% subjects were females. 56.2%victims belonged to rural area as compared to43.6% urbanites while residence of 0.2% males wasunknown.

Alleged cause of death in 42.6% cases was road

traffic accidents, 11.6% deaths were due topoisoning, 9.2% victims had died due to naturaldisease, 9% due to burns, railway accidents formed6.8% of the share and miscellaneous other causescontributed 20.8%.66.2% cases were observed in 21-50 years of agegroup in which rigor mortis lasted longer ascompared to 0-20 years (12%) and above 50 years(17.8%) age.Effect of temperature and humidi ty:In the months of April to June, fully developed rigormortis lasted from 11 hours 25 minutes to 28 hours25 minutes while in the quarter of July to September,

complete rigor mortis lasted from 17 hours 15minutes to 34 hours 20 minutes. The maximumtemperature during these months ranged from46.5C to 26.6C while minimum temperatureranged between 27.6C to 12C. Relative humiditylevels in these months varied between 95% to 31%as shown in figureI.In the months of October to December, fullydeveloped rigor mortis lasted from 16 hours 25minutes to 61 hours 5 minutes while from January toMarch it lasted from 19 hours 5 minutes to 50 hours15 minutes. The maximum temperature during thesemonths ranged from 35.4C to 13.6C while

minimum temperature ranged between 20C to 2.6and the relative humidity varied between 97% to65% as shown in Figure I.Time of appearance and disappearance: In thepresent study, it was observed that the averageduration for onset of rigor mortis was 8 hours and 39minutes. The maximum duration in which rigormortis had begun to appear in the body was 1 hourand 35 minutes while the longest duration by which

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rigor mortis had not completely appeared in the bodywas 24 hours.The average duration for fully developed rigor mortis

was 18 hours and 19 minutes, the shortest durationbeing 3 hours and 15 minutes and the longest 33hours and 40 minutes.The average duration for disappearing rigor mortiswas 34 hours and 36 minutes. The shortest durationby which rigor mortis had disappeared had 15 hoursand 30 minutes while one case was observed inwhich rigor mortis was presenting some parts ofbody at 70 hours and 35 minutes as shown inFigure I.

Fig. I: Showing Average Onset of Duration andDisappearance of Rigor Mortis

Sequence:In 94.6% cases rigor mortis was found to appear firstin the eyelids followed by lower jaw, neck, upperlimbs, trunk, lower limbs and lastly fingers and toes.It disappeared in the same fashion. However, in5.4% cases sequence was found to be erratic.Site of recovery: In cases recovered from openenvironment, the average duration of onset of rigormortis was early (6 hours 56 minutes) and averageduration of disappearance was also early (24 hours

44 minutes) as compared to dead bodies recoveredfrom closed environment.Nourishment:In the present study it was observedthat in well nourished individuals, the averageduration of appearance of rigor mortis was early (6hours 16 minutes) and it lasted for a short time (15hours 45 minutes) as compared tomoderately and

poorly nourished cases in which onset of rigor mortiswas late and it stayed for a longer period.Clothing: The average duration of onset of rigor

mortis (6 hours 50 minutes) and disappearance ofrigor mortis (27 hours 17 minutes) was earlier innaked dead bodies as compared to clothed victims.Muscular activity prior to death: It was observedthat in cases with history of muscular activity justprior to death the average duration of onset (8 hours5 minutes) was late while the average duration fordisappearance of rigor mortis (23 hours 33 minutes)was earlier as against those cases in which themuscles were at rest.Conclusion:In the hot weather from April to September, theaverage duration of onset was 8 hours 8 minute,complete rigor mortis lasted for an average durationof 18 hours 2 minute and average duration fordisappearance of rigor mortis during these monthswas 30 hours.In the winter months of October to March, theaverage duration of onset of rigor mortis was 7hours 25 minutes fully developed rigor mortis lastedfor 19 hours and 15 minutes and it disappeared atan average duration of 36 hours and 8 minutes.The usually taught standard rule of twelve does nothold true in every case as the process of rigor mortisis influenced by many variables especiallytemperature and humidity which has been optimalobserved in the present study. Much study has been

done on laboratory animals by various workers allover the world but a more systematic and detailedstudy is required on human subjects beginning rightfrom the time of death till the time of disposal. In acountry like India with wide variations of weather,post mortem interval each and every state needs tohave its own time table of rigor mortis so that itproves to be an effective tool for measuring post.

1-12 12-24 24-36 >36

Jan-March

Oct-Dec

July-Sept

April -June

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Average duration Site of recovery Nourishment Clothing IllnessMuscularactivity

Open

(38.80

%)

Close

d

(61.20

%)

Well(4.8

%)

Moder

ate

(90.8%)

Poor(4.4

%)

Naked(4

.8%)

Clothed

(95.2%)

Prese

nt

(8.6%

)

Abse

nt

(91.4%)

Prese

nt

(7.6%

)

Abse

nt

(92.4%)

Onset 6.56 7.22 6.16 7.16 7.27 6.50 7.20 5.59 7.36 8.05 7.21

Complet e 19.08 17.21 15.45 17.13 19.16 18.09 17.20 20.29 17.16 18.33 17.17

Disap pearan ce 25.44 34.08 30.51 29.30 27.17 30.15 39.10 28.32 23.33 31.03

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