This study was conducted at the Forensic Anthropology Laboratory of the Johannesburg Forensic Pathology Service Medico-legal Mortuary. Ethical clearance was provided by the Animal Ethics Screening Committee (clearance number 2013/19/01) and Human Research Ethics Committee (clearance number M130414).

The sample included five neonate pigs (Sus scrofa domesticus), ranging between one to three days old (Fig. 1). The pigs died from natural causes and were donated to the study by a local pig farm. No animals died for the purpose of this study. Pig carcasses were used as human proxies to test five maceration methods before isolating the best method, which was later tested on human infant remains. Pigs are a common animal model used as human analogues in forensic anthropological studies because porcine bone displays similarities in anatomy, morphology, healing, remodeling, density, and mineral concentration with human bone [11].

A neonate porcine carcass used to test maceration methods

The sample also included the fleshed remains of five deceased full term human neonates that underwent routine medico-legal autopsies at the Johannesburg Forensic Pathology Medico-Legal Mortuary. These remains were unclaimed and unidentified neonates that remained unclaimed after thirty days. Decedents that remain unclaimed after 30 days are typically buried by the municipality; however, these remains were approved for use in the study due to its benefit for future cases that will require maceration and forensic anthropological analysis. The skeletal remains were then archived in a forensic anthropology repository for unidentified unclaimed remains up until the time that they are identified and claimed.

The neonate pig carcasses were placed in a mortuary fridge for 30 days prior to maceration, to recreate the state of decomposition as the unclaimed infant human remains. All remains were skinned and eviscerated prior to their undergoing maceration.

Five maceration methods were tested on the pig carcasses (one pig per maceration method) to determine their effectiveness. The methods included invertebrate maceration by meal worms, chemical maceration by bleach, chemical maceration by borax solution, enzymatic maceration by laundry detergent and sodium carbonate solution, and chemical maceration by sodium hypochlorite. The length of time for each method varied and depended on how often the macerating agent required replacement. Due to the fragile nature of the juvenile bones, an additional defatting process was not implemented after the maceration process as is usually done with adult bones. A summary of the maceration processes are tabulated in Table 1.

Invertebrate maceration using meal worms [12] was achieved by placing the carcass into a plastic container of meal worms, which were covered with a bran bedding medium. The consumption of the carcass by the meal worms was reviewed every 24 h.

Chemical maceration using bleach [4] was achieved by disarticulating the pig carcass and immersing the remains in undiluted household bleach in a stainless-steel pan for 15-min intervals. The bubbling of the bleach and resulting heating up of the liquid indicated that the soft tissues were being chemically removed. After the completion of each interval, the remains were lifted from the bleach to monitor the progress of the maceration. Before being placed back into the pan for the next 15-min interval. During each interval, the used bleach was discarded and replaced with fresh household bleach.

Chemical maceration using sodium hypochlorite (SANS 10228) [13] was achieved by placing the disarticulated pig carcass in a stainless-steel pot, and the remains were immersed in sodium hypochlorite. Progress of the chemical maceration was checked at 15-min intervals.

Chemical maceration using a borax solution [14] was achieved by placing the disarticulated pig carcass into a stainless-steel pot and immersed in a solution with a concentration of 100 mL of powdered borax per 1 L of water. This chemical maceration method was combined with warm water maceration; therefore, the temperature of the solution was preheated and then maintained at a temperature of 75 °C and allowed to simmer, with progress of the maceration checked at 15-min intervals.

Enzymatic maceration using laundry detergent and sodium carbonate solution [1, 15] was achieved by placing the dismembered pig carcass into a stainless-steel pot and immersed in a solution with a concentration of 20 mL of powdered laundry detergent with active enzymes and 20 mL of sodium carbonate powder per 2 L of water. This enzymatic maceration method was combined with warm water maceration to aid the enzyme activity; therefore, the temperature of the solution was pre-heated and then maintained at a temperature of 75 °C and allowed to simmer, with progress of the maceration checked at 15-min intervals.

After each interval, the remains were removed from their maceration medium to determine if the soft tissues were soft enough for manual removal of the soft tissues from the bones by brushing. If bones could not be removed from the soft tissues, they were returned into their maceration medium for a new interval. This was repeated until maceration had been completed. Thereafter, the porcine bones were rinsed with tap water and allowed to dry thoroughly at ambient temperature beneath a fan.

A scoring method was created to assess the effectiveness of each maceration method. As outlined in Table 2, numerical scores were assigned to common observations seen in all the tested maceration methods. A score ranging from 1 to 5 was assigned to four variables assessed in each method: soft tissue breakdown, bone exposure, bone condition, and odor intensity. The scores were assigned after maceration was completed. The four scores assigned to each sample were added for a total score, which indicates the overall effectiveness of the maceration method. Higher scores indicate greater effectiveness of the respective method. The maceration method that scored the highest was then repeated on five human infant remains to validate its effectiveness in human remains.