Superabsorbent Polymers gave Forensic Scientists a real headache-until now

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It’s a sad fact that progress in one area throws up unexpected problems somewhere else.  Such is the case with Forensic Scientists and Super Absorbent Polymers (SAPs). Invented in the 1960s, SAPs are just brilliant at soaking up and holding onto organic fluids of all kinds. Concrete protection, sewage, waterproofing cables, there wasn’t anywhere they couldn’t go or do. In things like nappies and sanitary products they were a godsend. And that’s where the problem started for Forensic Scientists.

As fans of modern crime dramas will know, DNA technology has been the biggest breakthrough in Forensic Science for a hundred years. It allows reliable convictions from tiny samples, and the construction of enormous databases, both of which have facilitated the solution of horrible crimes like murder, rape and sexual assaults. The trouble is that some of the best evidence may be lying on products containing SAPs. And they just won’t give up organic products, especially things like semen. Existing techniques were able to wash semen from the upper layers of SAP containing items, but that was all.

Now Dr Anna Marie O’Connor and Professor Joy Watts of the University of Portsmouth have developed a new technique called SAPSWash which allows the recovery of sufficient spermatozoa to provide completely reliable DNA profiles from things containing SAPs.  By experimenting with solutions of calcium chloride (CaCl₂) the scientists have been able to get down into the deep SAP gel where the majority of evidence was absorbed.  They consistently extracted enough DNA Material for all standard practice. And for an age of tight budgets, the authors claim: “The SAPSWash method has delivered an efficient, cost effective process which could be relatively easily implemented into current, mainstream forensic laboratory practices, using standard, inexpensive consumables.”

The implications are not just for police and forensic investigators however. Victims will know that another step has been taken towards safe and reliable convictions. Intending criminals, take note.

For copyright reasons, we can’t hyperlink to Anna-Marie’s paper this time. But here is the reference if you want to look for yourselves. The Science Direct portal is always a good link to papers on all topics.

A-M.O’Connor J.E.M.Watts  The development of a rapid and reliable method (SAPSWash): For the extraction and recovery of spermatozoa from superabsorbent polymer containing products Forensic Science International Volume 316, November 2020, 110501

We would like to offer our thanks to Dr O’Connor and Professor Watts for their help and and advice with this, the first story where LSS actually breaks news. You read this news first at LSS.

#forensicscience #dna #sapswash #universityof portsmouth #crimescene #rape #sexualassault #SAP