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Human and non-human identification of unknown skeletal remains is of great importance in forensic and anthropologic contexts. However, the traditional morphological methods for bone species identification are subjective or time-consuming. Here, we utilized Fourier transform infrared (FTIR) spectroscopy and chemometric methods to determinate the spectral variances between human and non-human (i.e., pig, goat, and cow) bones. To simulate real forensic situations as much as possible, fresh, boiled, and decomposed bones were included in this study. Principal component analysis (PCA) results illustrated pig bones were more sensitive to the environmental and external factors than other species studied in this work. Thus, pig bone might not be a suitable proxy for human bone in the study of postmortem changes. More importantly, score plots of PCA results showed clear separation with a slight overlap between the human and non-human fresh bones, but it failed to distinguish the boiled and decomposed bones. Then, partial least squares discriminant analysis (PLS-DA) was employed, and both internal and external validations were conducted to assess its classification ability, which resulted in 99.72 and 99.53% accuracy, respectively. According to the loading plots of PCA and PLS-DA, the spectral diversity was mainly due to the inorganic portion (i.e., carbonates and phosphates), which can remain relatively stable under various conditions. As such, our results illustrate that FTIR spectroscopy could serve as a reliable tool to assist in bone species determination and also has great potential in real forensic cases with natural conditions.

Acute aortic dissection (AAD) is the most common cause of sudden unexpected death related to aortic diseases. A retrospective study of 31 sudden unexpected deaths caused by AAD was conducted at Xi'an Jiaotong University Forensic Center from 2001 to 2012. We summarized the forensic characteristics of AAD and assessed the clinically diagnostic accuracy of AAD. The characteristics of sudden unexpected death due to AAD were male predominant (male: female=6.7:1), relatively young with the mean age of 44, and predominance of type A dissection (77.4%). Cardiac tamponade was the most frequent cause of sudden death (87.1%). Of the 31 cases, 26 (83.9%) patients were not recognized clinically and were misdiagnosed with acute myocardial infarction, coronary artery disease, cholecystitis, acute gastroenteritis, renal/urinary lithiasis, or acute pancreatitis. In summary, AAD can be difficult to recognize, diagnosis is therefore sometimes delayed or missed. The medicolegal death investigation can help physicians have a better understanding of AAD.