What we know about the genetic investigations
This article is an attempt to reconstruct a timeline of the genetic investigations in the Yara Gambirasio murder case.
This is not an easy task, on the one hand because they have undoubtedly been complex, entrusted to multiple individuals and agencies and lasted for years, on the other hand because not even a trial an effort was made to perform such a systematic reconstruction, ordering testimonies and investigation results in a easy to consult summary.
We will therefore have to rely on the media, which indeed are not always reliable, nor precise or totally coherent among them.
We will hence try to establish some events as sure and point out others as uncertain or doubtful.
April – The trace subsequently attributed to Silvia Brena is found by the RIS on the right cuff of the jacket donned by Yara. It seems that this trace reacted positively to a presumptive test for blood, but not to a confirmative one.
May – The RIS collect the set of traces on Yara’s panties and, partially, her leggins, which will be first attributed to Unsub1 and later to Bossetti. The source of the trace has never been ascertained.
Sampling and analysis by the Scientific Police of the DNA of 476 regular clients of the Sabbie Mobili discotheque, located a few hundred meters from the place where Yara’s corpse was found.
Damiano Guerinoni, nephew of Giuseppe Guerinoni, is called back from Peru exclusively for one such sampling, even if he was already abroad on November 26, 2010.
In the following years the Scientific Police will reconstruct en masse thousands of other DNA profiles of local people, according to some sources at least 7-8000.
The grand total of the collected samples will be over 22000.
September – On the 22nd day of the month prosecutor Ruggeri entrusts Colonel Lago (head of the Parma section of the RIS) with analyzing the mitochondrial DNA of traces 31G20 and 31G19 to determine part of the somatic characteristics of Unsub1. Lago will in turn pass this task to the University of Florence, whose experts will state that they were unable to obtain any result because of the deteriorated state of the trace.
October – A Y-haplotype matching is found between Damiano Guerinoni and Unsub1, this match will lead the investigator to determine that the real father of Unsub1 (and hence of Bossetti) is Giuseppe Guerinoni, a bus driver deceased in 1999.
March – Novelli and Giardina, from the Tor Vergata University in Rome, announce that Giuseppe Guerinoni is Unsub1’s father with a 99.87% level of confidence, while in a first announcement in December 2011 they had set that level of confidence at 87.39%.
July/August – Giardina is entrust with examining the mitochondrial DNA from 532 mouth swabs taken from as many women and men (the latter being about 100) to compare it with Unsub1’s (mitochondrial) profile. Unfortunately, however, he is given Yara Gambirasio’s mitochondrial DNA profile as reference and so he will not find any match.
February – Also thanks to pressures from the Gambirasio family and their DNA expert Portera, prosecutor Ruggeri entrusts Previderè, from Padua University, with analyzing the body hair samples found on Yara’s corpse to establish their origin (human or animal) and to obtain mitochondrial DNA profiles from them.
February – Law enforcement entrust the Center for Genomic of the Saint Raphael Hospital in Milan with the task of sequencing Unsub1’s genome, with the aim of, according to an interview by Portera to the Eco di Bergamo, “reconstructing the DNA sequence, hence not just the 15 STR (Short Tandem Repeat) regions usually employed for forensic testing“. The results of this research are not available. Take notice that 15 STR were cited, not 21 as in the final report by Previderè.
November/December – (Uncertain) Previderè realizes, thanks to a test with a sample obtained from the victim’s femur, that Giardina compared the mtDNA from 532 samples with Yara’s and not Unsub1’s reference profile.
February – The nuclear DNA testing of the 532 samples already tested for mitochondrial DNA starts. The task is assigned to Previderè, with the help of researcher Grignani.
The research goes on for three and a half months, even if it has been speeded up by filtering the profiles according to the presence or absence in them of a rare allele (26) at the SE33 locus, present in Unsub1’s nuclear DNA profile.
Day 13 – It is ascertained that the nuclear DNA profile of Ester Arzuffi is that of the mother of Unsub1.
Day 15 – Through a purported alcohol test on the street, a saliva sample is obtained from Massimo Bossetti. Arzuffi’s other son, Fabio, had already been previously excluded, since Giuseppe Guerinoni is not his father (different Y-haplotype).
Day 16 – Massimo Bossetti is arrested for the murder of Yara Gambirasio.
January – At the end of the month Previderè delivers his report, in which he certifies that the mitochondrial DNA of Unsub1/Bossetti is absent from the 31G20 trace.