M.A. Theses: Jacqueline B. Duffy, 1991

An Appraisal of the Stability of Sex Chromatin and the H-Y Molecule in Forensic Contexts

Forensic investigations may involve recovery of remains so severely damaged that gender can no longer be determined from macroscopic examination of hard or soft tissue. In this event gender differentiation can sometimes be accomplished at the microscopic level by cytological probing of remnant tissue. This investigation is aimed at the application of such cytological sexing procedures to som simulated forensic environments.

Two procedures were developed using human tooth pulp tissue, one detecting X and Y chromatin in the cell nucleus and the other detecting a male molecule, histocompatibility-Y (H-Y) located on the cell membrane. Simulated forensic environments included burial of teeth, exposure on the surface, storing teeth at room temperature, and heat treatment. The jaws and heads of pigs (Sus scrofa) substituted for human tissue for the comparison of environmental effects on pulps from extracted teeth versus pulps from unextracted teeth.

Stained X and Y-chromatin discriminated gender for no longer than two weeks in teeth buried or exposed out of doors. No substantial difference in decomposition rates was recorded between human and pig extracted dental pulps, and pig unextracted dental pulps in outdoor environments. In teeth held at room temperature, sex chromatin remained stable for more than one year. The pulps of extracted human teeth, subjected to temperatures above 100C over a period of one hour, lost endonuclear granulation and with it sex chromatin staining characteristics, whereas pulps in unextracted pigs teeth retained nuclear granularity after exposure to temperatures of 300°C over the same period. A maximum temperature, reached but not sustained within the human or pig pulp chamber, at which sex could still be diagnosed, was assessed by a thermocouple probe to be 50°C. Unextracted pig's pulp chambers registered this temperature in an open fire, when the temperature of the fire reached 600-700C. H-Y, detected by immunocytochemical staining, proved to be highly unstable, rapidly losing antibody binding capacity in any extracorporeal environment.

The results of the study indicate that whereas a cytological mode of sex discrimination has potential application to any forensic situation, its most common application is likely to be to situations where recovery of remains is fairly rapid, as in mass disaster or fire. Forensic tissue samples submitted for analysis should be stored as found without any fixative or fluid additive, and transported packed in ice.