Water's Oxygen Content Clears Suspected Murder Weapon, Fingers Other

The oxygen content of water helped forensic engineer Ken Russell, who writes the Calamities Column for Design  News,  identify a possible murder weapon disposed of by monkeys, in this case of a hit ordered by the head of the New England La Cosa Nostra. There was no prosecution for 15 years until police divers, acting on testimony from one of the suspected killers, recovered two pistols from Canada Pond in Rhode Island.

Ken was asked whether either the .32-caliber automatic or .38-caliber revolver could have spent 15 years underwater.  With the help of  an electron microscopy expert, replicas of the insides of the two gun barrels were made for study under the scanning electron microscope.

The inside of the .38-caliber pistol was badly corroded. The inside of the .32-caliber barrel was nearly pristine, as shown in the photo of the replica, above.

The determining factor in corrosion rates of steel is not temperature, acidity or saltiness, and, moreover, composition of the steel is only a minor factor (except for stainless steel). Oxygen content of the water is the crucial factor. At Ken’s request, divers measured the oxygen content in the region of the pond where the guns were recovered. The water was saturated with oxygen, and the corrosion rate of the steel could be estimated at about 1/100 inch per year.

Ken concluded that the badly corroded .38-caliber gun had spent 10 or 20 years in the lake — a possible weapon in the murder case.  The .32-caliber gun had spent, at most, about a year under water. So, perhaps, the evidence in another yet-to-be-solved case, that concidentally found its way to a popular dumping ground?

This article appears in its entirely in the Calamities Section of Design News.