Assessment of the Forensic Genetic Tests Conducted by the Scientific Police on Item 165B (Bra Clasps)

From what has been explained above, we can draw the following conclusions about the analytical procedures performed on Exhibit 165B.

– Regarding the nature of the material taken from the item, there does not exist evidence which scientifically confirms the presence of presumed flaking cells. Hence the hypothesis formulated by the Technical Consultant about the nature of the material taken from Exhibit 165B is wholly arbitrary in that it is not supported by objective findings;

– From the electrophoretic graph relative to the autosomic STRs, we can assert that relative to the markers D8S1179, D21S11, D19S433, D5S818, there was an erroneous interpretation of the peaks present in the electrophoretic graph in that peaks were considered stutter whose height was above 50 RFU (D19S433 peak 14↑54), exceeded the threshold of 15% of the major allele (D8S1179, D21S11, D5S818), or were not in stutter position (D5S818), and thus should have been considered alleles. It follows from this that in the DNA extracted from Exhibit 165B are present several minor contributors that were not revealed by the Technical Consultant;

– The electrophoretic graph relative to the Y chromosome markers shows, besides the peaks indicated in the RTIGF as alleles, the presence of additional peakswith heights that exceed the threshold of 50 RFU which, despite not being in stutter position, were not taken into consideration by the Technical Consultant. It follows from this that in the DNA extracted from Exhibit 165B are present several minor contributors which were not revealed by the Technical Consultant, confirming what was already observed in the electropherograms of the autosomic STRs.

– We find that the Technical Consultant arrived at this restrictive conclusion (presence of only two individuals: victim and Raffaele Sollecito) following an incorrect interpretation of the autosomic STRs as a result of having disregarded the recommendations of the ISFG concerning the correct interpretation of mixtures, recommendations which, had they been followed, would have allowed one to conclude that several minor contributors were present in the trace besides the victim’s profile (major contributor). Hence we agree with Dr. Stefanoni’s statement regarding “the extrapolation of a genetic profile deriving from a mixture of biological substances belonging to at least two individuals, at least one of male sex” but we cannot accept the conclusion stating that “the genetic profile is compatible with the hypothesis of a mixture of biological substances (presumably flaking cells) belonging” only “to Raffaele Sollecito and to Meredith Susanna Cara Kercher” insofar as, from what has been explained above, a mixture is present in which several contributors of male sex are present (a circumstance supported by the electropherogram relative to the Y chromosome, where several alleles are clearly present which, despite being particularly evident, were not taken into consideration by the Technical Consultant);

– The item was recovered 46 days after the crime, in a context highly suggestive of environmental contamination. The risk of incorrectly interpreting such environmental contaminatns from dust could have been minimized only by taking the care [avendo l’accortezza] to institute extremely stringent control procedures, including the analysis of extracts from sterile cotton swabs soaked with sterile buffer passed on ambient surfaces to take samples of dust, a procedure which was not carried out;

– Taking into account what has been explained relative to the inspection methods, having seen the documentation in the record, and in particular the DVD of the filmed investigation of the scene [indagini di sopraluogo], the official photos of the Scientific Police, and the statements made in court, we find that the universally noted inspection procedures and correct protocols of collection and sampling of items were not applied on Via della Pergola, even [those designed] to minimize environmental contamination and contamination from handling. From this it follows that it cannot be ruled out that the results obtained from Exhibit 165B derive from contamination phenomena in any phase of the collection and/or handling of the item.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: