Flow cytometric evaluation of postmortem pulp DNA degradation

During postmortem autolysis, cellular organelles and nuclear DNA break down into their constituent parts. DNA flow cytometric analysis was applied to study the denaturation of splenic cell DNA as a possible method for postmortem interval determination. DNA denaturation continued for 72 hours at a constant rate, with no intact DNA peaks thereafter. The value of using dental pulp tissue for flow cytometric determination of postmortem interval was investigated. The pulps of 57 routinely removed impacted third molars from patients 15 to 30 years of age were obtained. Pulp tissue was removed at 24, 48, 72, 96, 120, and 144 hours postextraction. Debris (degraded DNA) was defined as all signals left of the standardized mean 2n peak and expressed as a percentage of the total number of signals. In contrast to the splenic cell DNA, dental pulp tissue exhibited minimal DNA degradation by 144 hours postextraction, and no constant relation was found between time and DNA degradation during this time. In this study, pulp tissue was found to be unreliable to determine the early postmortem interval but might be of greater value in the later stages.     

Consistency amongst pairs: How consistent are child co-witnesses with one another?

Purpose

When multiple children are asked about the same event, the consistency of their reports may be used as a heuristic for credibility. Little research has considered how consistent child co-witnesses are likely to be. In this study, we explored how likely child co-witnesses were to report the same details from a mutually experienced event.

Methods

Pairs of children participated in an educational science event during which the target attempted to coax the children into breaking preestablished rules for the session (i.e., commit transgressions). Children were individually interviewed about their experience on two subsequent occasions.

Results

Co-witnesses tended to be quite inconsistent: 32%–55% of all details recalled were only mentioned by one co-witness. Various factors were associated with co-witness consistency, including delay before the interview, centrality of details recalled, and children's age and forthcomingness.

Conclusions

The findings indicate that inconsistency between co-witnesses reflects a natural memory phenomenon, and that practitioners should be cautious of using co-witness consistency as an indicator of credibility.