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Scientist concluded that Grangegorman investigation findings may have arisen because of contamination in forensic lab, jury hears

Date
2015-03-30

Stage
Trial

Primary locality
Dublin

County
Dublin

Summary

In a murder trial at the Central Criminal Court, forensic scientist Dr Philip Avenell testified that DNA profiles of two victims, Sylvia Shields and Mary Callanan, found on a black velvet jacket belonging to the accused, Mark Nash, could have arisen from contamination in the forensic laboratory. Avenell compared two hypotheses: DNA obtained when the jacket was present at the murders or when it was seized. He could not determine which was more likely. He cited possible contamination from packaging, lack of bag wiping, examination of blood‑stained items six weeks apart, and file‑to‑file transfer. Avenell concluded that the scientific findings might have resulted from lab contamination. The judge ended the evidence, resuming the case on 14 April 2025. Mark Nash pleaded not guilty.

Who, what, where, when and why

What: Report matter: Scientist concluded that Grangegorman investigation findings may have arisen because of contamination in forensic lab, jury hears. Charges or matters: murder of Sylvia Shields; murder of Mary Callanan. Procedural stage: trial

When:

March 6 Hearing Or Sentence
March 7, 1997 Hearing Or Sentence
Tuesday April 14 Other
April 20 Other
2015-03-30 Publication

Why: Dr Avenell told the court that because wiping down the bag containing the jacket wasn't a standard practice in 1997, this was another possibility of contamination as blood flakes or particles could transfer to the item. CNI source report