Genetic analyses on bone remains in the field of human identification represent one of the most stimulating and complex challenges for forensic geneticists. Unlike the analysis of biological traces such as blood, semen, saliva or urine, that usually do not present any particular technical and operational difficulty so that personal identification can be achieved, as appropriate, more or less easily through comparing the genetic profile obtained from the sample with the one available as reference, the identification of bone remains forces the analysts to face multiple and complex variable factors (e.g. the degradation of genetic material and the environmental contamination of the samples) that can affect the success of the analysis in the sense of obtaining a complete and interpretable STR profile. In such cases an accurate evaluation of the characteristics of the sample and the environmental conditions to which this finding has been exposed is extremely important.
This presentation describes the methods used in the Laboratory of Forensic Genetics of the Department S.A.I.M.L.A.L of the University of Rome "Sapienza" for the analysis of bone remains, to the purpose of either personal identification or the assessment of a parental relationship.
The authors will present a selection of 20 cases came under their observation during the years 2007-2011, for which the genetic analyses were performed on different bone samples (femur, tibia, humerus, mandible) using different extraction, amplification and STR typing methods. The results obtained will be compared in order to assess for each case the specific role of 3 important variable factors: the age of the remains, the environmental conditions of storage/finding and the cause of death.
6 out of the 20 cases showed interpretation problems related to the Low Copy Number (LCN, or Low Template -LT) DNA condition due to DNA degradation (i.e. the effects of high temperatures in case of charred remains; the acceleration of autolytic processes in case of hexumation of a corpse) and/or the presence of DNA inhibitors (e.g. Calcium Phosphate, Humic Acid) that likely were co-extracted with the DNA from the evidence sample. The results show that the possibility of obtaining a complete and interpretable genetic profile depends largely on the 3 variable factors mentioned above, particularly with regard to the environmental conditions of storage/finding of the remains, thus confirming the need to optimize the analytical methods in order to minimize the effects of environmental inhibitors.
After attending this presentation, attendees will understand some principles of genetic analysis on bone remains, the challenges related to this kind of investigation especially for what concerns criminal cases and the importance of the honesty of the forensic scientist when a certain and unequivocal interpretation of the DNA profile obtained cannot be provided.
This presentation will impact the forensic community by highlighting the importance of bone remains as an evidentiary sample in forensic caseworks and the difficulties related to the genetic analysis of such samples due to degradation and/or inhibition factors: in these cases it is fundamental for the scientist to consider that asserting that a complete and interpretable genetic profile is not obtained from a sample (thus the sample cannot be considered useful for a comparison) does not mean a failure but, on the contrary, reveals scientific honesty and should stimulate the necessary progress in this field
