Aging of Lesions

Abrasions

Histologic examination of abrasions may be used to roughly estimate their age, based on the general sequence of events of wound healing (hemorrhage, infiltration of leukocytes, and regeneration and fibrosis), and bolstered by species-specific knowledge of infiltrates and processes, where applicable (Gerdin, 2014; Gerdin & McDonough, 2013).

Generally there are considered to be four stages of healing: scab formation, epithelial regeneration, subepidermal granulation, and regression (Ressel & Ricci, 2016; Roberston & Hodge, 1972; Touroo, 2012). A guideline for time intervals for each stage is: scab formation, 0-12 hours; epithelial regeneration, 30-72 hours; subepidermal granulation, 5-12 days; and regression, more than 12 days (Ressel & Ricci, 2016; Roberston & Hodge, 1972; Touroo, 2012). Caution is advised in using this general guideline to assess the age of a lesion, as the effects of variables such as species variability, incidence of self-trauma, malnutrition, protein deprivation, and disease are not fully known and may be challenged in a court setting.

Contusions

In both medical and veterinary forensics, there has been longstanding interest in the aging of contusions. As discussed above, contusions go through stages of development from the initial BFT, through the migration of the red blood cells (RBCs) of the hemorrhage via the path of least resistance and gravity, to appearance near or within the skin layer where the contusion may or may not be visible. The change in oxygenation levels of the RBCs and then the metabolism and subsequent production of byproducts of the RBCs result in the color changes in bruises.

Controversy exists as to the reliability and accuracy of aging contusions based on their visual appearance. Langlois extensively reviewed the range of colors often attributed to bruises along with the physiologic processes that may account for these changes in humans. He discussed the use of spectrophotometry to assess contusions and detailed the limitations of relying on visual assessments (Langlois & Gresham, 1991; Langlois, 2007).

Observations of the visual appearance of contusions in specific animal species have been made. Munro references a study in which bruises in cattle and sheep were documented to be red and hemorrhagic between 0-10 hours, becoming dark colored by 24 hours, having a watery consistency by 24-38 hours, and then appearing to be rusty orange in color with a soapy texture when more than 3 days old (Gracey et al., 1999; Merck, 2013; Munro & Munro 2008, 2013). Other authors state that visual assessment of bruises as a method to determine the age of a bruise has been shown to be unreliable (Barington & Jensen, 2013; Grossman et al. 2011; Pilling et al., 2010).

Histology may assist in the general evaluation of a contusion to estimate whether the lesion is very recent (less than 24 hours), recent (12-24 hours), or more than a few days old (more than 48 hours) (Gerdin, 2014; Gerdin & McDonough, 2013). Evaluation of the histologic appearance, progression, and healing associated with contusions in some animals has been published. Research on the estimation of the age of bruises in pigs is generally based on studies of wound healing (Barington & Jensen, 2013). Studies show it is possible to estimate the age of bruises in pigs to be more or less than 4 hours. For bruises more than 4 hours old in pigs, an age of the contusion can be estimated based on the pattern of cell infiltration and by comparing the reaction to wound healing (Oehmichen, 2004; Raekallio, 1980). The average number of neutrophils in the subcutis and the average number of macrophages in the muscle tissue correlated with the age of the bruises. In addition, the localization of leukocytes in muscle tissue was also time dependent. Using this information, bruises could be determined as being either less than 4 hours or between 4 and 10 hours of age in pigs (Barington & Jensen, 2013).

Similar studies have been done using lamb and calf carcasses sent for slaughter. McCausland and Dougherty (1978) established histologic criteria for aging contusions for up to 48 hours. The criteria considered the presence and relative numbers of polymorphonuclear leucocytes, macrophages, fusiform cells, and new capillaries. This study found that the microscopic criteria were the same in the two species and concluded that the yellow color present in contusions that were approximately 48 hours old was useful in the aging of these lesions in calves and lambs.

In addition to the age of the lesion, the force of the impact may also affect the histologic findings. One study found that the impact force significantly influenced the severity of hemorrhage and amount of necrotic muscle tissue. The number of neutrophils in the subcutaneous tissues was increased with increasing age of bruises and impact force. The author of that study argues that in the case of BFT, whenever possible, the underlying muscle as well as the subcutis should be evaluated. The study also found that the number of macrophages in the muscle tissue was relevant for age determination only in contusions resulting from the highest forces. Therefore, forensic histologic evaluation of contusions should consider the impact force as well as timing of the blunt force trauma incident (Barington et al., 2016).