Henssge nomogram typesetting error

Abstract

The Henssge nomogram technique for estimation of post mortem interval (PMI) utilizing body cooling is used worldwide by forensic pathologists (FPs) who may photocopy the nomogram from a popular source such as the textbook Knight’s Forensic Pathology [1, 2] to calculate the PMI. The relationship of the components of the nomogram to each other is crucial for accurate calculations. Any alteration from the exact spatial layout will result in significant error. In recent cases, different FPs determined the PMI independently and observed significantly divergent answers for each case. Careful scrutiny of the calculation process showed that the only variable in the processes was that nomograms were copied from two different sources: one from Forensic Pathology by Knight and Saukko (FPKS3) [1], and the other from Knight’s Forensic Pathology (KFP2) [2]. The latter version is similar to that in the 1 edition of this text, as well as in a paper by Henssge et al. [3]. In one high-profile case, the ambient temperature was 24 C and the rectal temperature (RT) 33 C. With corrective factors, the nomogram in KFP2 showed the PMI as just over 19 h, while the nomogram in FPKS3 gave an estimated PMI of 16 h 30 min. Using the same values in an electronic version of the equation resulted in a PMI estimation of 19 h 10 min. This represents a 13 % difference in PMI between the nomograms in KFP2 and FPKS3. Careful study of the two versions of the nomogram led us to discover differences in the typesetting of the diagrams. This was visually illustrated by superimposition of the two scanned nomograms in KFP2 and FPKS3 (Fig. 1). These variations suggest to us that the nomograms printed in the textbooks mentioned are not exact replicas of the original. We do not believe that the nomogram published in the original journal [4] suffers from these spatial defects, as similar results are found when results from this nomogram are compared to those from the calculation. However, it is suggested by some, and we strongly recommend, that the nomograms reproduced in any printed format be used cautiously, and at least be correlated with a different source and/or an electronic version of the equation. These electronic resources based on the original Henssge equation are available as, among others, a web based resource [5], and Apple and Blackberry apps in the respective e-markets. The editors are aware of this problem (personal communication—email communication with Bernard Knight) and we understand that any future editions will contain a note regarding this.