Alcohol intoxication is a major contributor to fatal falls. There is an increasing risk of falls at increasing BACs. It increases body sway and impairs visual tracking for guiding steps. Alcohol also potentiates orthostatic hypotension. As such the accurate determination of blood alcohol concentration is important in fatal fall victims as illustrated in the following case report.

Case Report

A 31 year old man was found dead several hours later after a fall from a great height in a Northern Ontario city. At autopsy the next day, peritoneal cavity blood and urine samples were collected. The blood was placed in a jar without preservatives and the urine in a tube with 1% NaF as a preservative. Nineteen days later the samples were received at the Centre of Forensic Sciences in Toronto. Alcohol analyses were conducted by headspace GC using t-butanol as an internal standard.

The blood was found to contain 0.096 g/100mL and the urine contained no alcohol. In addition the blood contained elevated acetaldehyde and 0.004 g/100mL n-propanol concentrations (see above GC output)

Biomarker of Putrefaction

N-propanol has been found to be a marker of postmortem production of alcohol. It has been suggested that the ratio of alcohol produced to n-propanol is 20 to 25:1. (see blog posted January 11, 2013) This would indicate that all the alcohol in the blood was formed postmortem

Other factors which would show that the postmortem alcohol concentration detected was unreliable were the zero UAC, the lack of preservative in the blood sample, the long delay in transit, and that the blood was collected from the chest cavity.

Warning Signs of Possible Postmortem Changes in Blood Alcohol Concentrations

Blood not taken from the femoral (leg) vein, instead blood is collected from the chest cavity (including cardiac or heart blood). Blood collected from the chest area is more prone to bacteria/microorganisms and alcohol diffusing from the gut. In addition blood from the chest cavity have a much higher glucose concentration as sugars are released from the liver, and thus encourage a false positive postmortem BAC.

A delay of several days or more between death and the collection of the blood sample increases the risk of putrefactive production of alcohol

No other samples such as vitreous humor or urine collected. These samples in general have no significant sugars and are more isolated from the gut and are more resistant to putrefactive changes.

No preservative such as sodium fluoride (NaF) in at least a 1% concentration. Once the blood is treated with NaF, it does not necessarily have to be refrigerated in transit.

Other volatile compounds detected in the blood such as acetaldehyde, acetone, isopropanol and n-propanol ( i.e. “a dirty chromatogram” as above).

Unusual physical characteristics of the blood such as coloration ( green or black) and viscosity(very thick or watery).





Conclusions

It can, therefore, be concluded that the postmortem BAC of the above noted case was inaccurate and that the victim was not intoxicated by alcohol before the fatal fall. Since n-propanol is a potential biomarker of putrefaction it should not be used for postmortem GC alcohol analysis. In comparison to the previous posting, the urine was a more reliable sample than the postmortem blood.

References

"Wigmore on Alcohol, Courtroom Alcohol Toxicology for the Medicolegal Professional", Chapter 6.05 Falls, Irwin Law Publishing, 559 pp, 2011 www.wigmoreonalcohol.com





Wigmore, JG, and Chow, BLC, "Case Report: Detection of Neo-Formation of Ethanol in a Postmortem Blood Sample Using N-Propanol and a Urine Sample", CSFS Journal, 33: 145-149, 2000









YouTube Video

Watch more about forensic alcohol toxicology at https://youtu.be/cxgz6fXxWxo