After returning from a trip around a lake in the eastern U.S. and docking the twin-hull pontoon boat they were riding in, three boys decided to jump in for a swim. The afternoon dip turned tragic, though, when two of the boys seized up as soon as they entered the water, reportedly paralyzed by electric current in the water. Unable to move, they drowned. The third boy was pulled to safety by a friend.
At the request of his father, who owned the boat, one of the boys had plugged one end of a modified AC extension cord into a shore AC receptacle and the other end into a duplex AC receptacle mounted on the pilot console of the boat before entering the water. Reportedly, the duplex receptacle mounted on the boat's pilot console was wired to another duplex receptacle mounted underneath a folding seat located at the stern of the boat, which served as an AC power source for two portable battery chargers.
The police initially determined that the boat owner had improperly wired the craft and was negligent, but they chose not to prosecute. The parents of the children who died, however, filed a lawsuit against the father, the local property owners association, its management company, and a sub-association. Counsel for the defense retained me to conduct my own research and determine the validity of the claims made by the plaintiff's expert witness. And a closer look at the case revealed more about what didn't happen than what did.
Beyond a reasonable doubt. I was brought in months after the initial evidence gathering, and the lack of documentation of the accident scene made it difficult to conduct a thorough forensic investigation. No one bothered to trace out or document the circuit and system details as they existed on or about the day of the incident. For the purposes of determining the cause of the drownings, the lack of concrete information created several problems and led to incorrect assumptions by the plaintiff's expert witness.
He claimed that corrosion found on the hull of the boat was indicative of the long-term presence of 120VAC leakage current and therefore proved that the water around the craft was charged with hazardous voltage and current that ultimately paralyzed the boys and caused them to drown. This assertion was incorrect on two counts. The type of corrosion he referred to is caused by direct current, not alternating current. In addition, photographs of the boat's hull taken after the accident depicted a type of corrosion typical to the marine environment and owing nothing to stray current leakage. To determine the type of corrosion beyond a shadow of a doubt, it would have been necessary to conduct laboratory testing using scanning electron microscope technology and laboratory destructive analysis method, neither of which took place. These incorrect assumptions threw doubt on the testimony of the plaintiff's expert.
Photos of the boat show two conductors ostensibly emanating from the battery compartment at the stern of the boat and hanging in such a location that they could easily come in contact with the water (Photo 1 above). If these two conductors were connected to any of the boat batteries, then the necessary condition to facilitate stray current corrosion would exist as the direct current source from the batteries would be in relatively close proximity to the metallic hull. However, the photos showed no noticeable consumption of the aluminum hull in the proximity of the two conductors, so there's no foundation to suspect the presence of a stray current corrosion condition. But more importantly, the connection of these two conductors was never established.
Questions also arose regarding the connection and function of the GFCI device that supplied power to the circuit feeding the boat dock. The plaintiff's expert claimed the circuit never had GFCI protection, but a GFCI in the boat owner's home was identified as supplying power to the dock receptacles.
The defendant reported that prior to the incident the receptacle was accidentally painted over, necessitating removal of the device for cleaning. He used an air compressor to blow out the paint, and when tested later by a county building official, the GFCI “tripped” correctly. When the owner “blew out” the paint with compressed air, it's very likely that he also introduced moisture into the device, which presented another possible contaminate to the GFCI circuitry, which could have affected its overall operation and reliability.
The plaintiff's expert rendered the opinion that GFCIs are designed to trip at between 3mA and 5mA, and that at 5mA GFCIs are designed to trip within 50 to 60 milliseconds. However, the UL 943 criteria governing GFCI trip times shows 5mA to be below the bottom trip-current published value of 6mA, in which case there can be no expectation for GFCI tripping reliably at values 5mA or below. When asked if he would consider a GFCI device defective if it failed to trip within 2 to 3 seconds at 5mA leakage current, the plaintiff's expert responded that he would determine that device to be defective.
Another theory presented by the plaintiff's expert witness held that a reverse-wired 120V extension cord (Photo 2 above) to the boat contributed to the accident. A model presented by the plaintiff's expert for both the hot and neutral current return paths showed a short-circuit condition resulting across the boat's accessory battery system. Under such a scenario, either the branch circuit breaker would have tripped immediately, mitigating any opportunity for electrical shock, or the connected boat conductors would have burned and suffered notable and substantial over-temperature and/or fire damage. Yet no evidence exists for any such condition.
A second theory regarding the wiring evaluated the possibilities of inadvertent connections and interference with GFCI protection as a possible cause. A loose strand connecting the neutral conductor from the house to the boat's DC positive terminal was the center of the theory (Photo 3 above). But once again, a model of the theoretical wiring scheme showed that either the branch circuit breaker would have tripped immediately and mitigated the opportunity for electrical shock, or the connected boat conductors would have burned up and suffered notable damage. Therefore, the stray conductor, if connected, served no role in the accident and doesn't offer any conclusive data as to the status of the GFCI device or on current leakage conditions or current paths into the water.
Additionally, no evidence of a high resistance fault, parting arcing, or heating connection on the receptacle's brass terminal screw receptacle was observed or reported as a result of my inspection. There was no physical evidence showing the loose conductor strand ever having come in contact with the adjacent terminal, and thus no basis to believe or conclude that this ever occurred.
In the end, the lack of evidence gathered immediately after the incident made it impossible to draw a clear conclusion as to the origin and cause of the electric shock. However, according to U.S. Coast Guard casualty data, defective battery chargers, or use of unapproved “marine rated” battery chargers in such situations are frequently implicated in “swimmer” electric shock incidents — issues never evaluated by the plaintiff's expert.
The data collected and the findings made by the electrician who assessed the system on or about the day of the incident weren't consistent with the information and electrical architecture considered as possible in this case. But more importantly, two lives were lost without explanation because of a failure to properly document evidence.
Ruggieri, P.E., is a forensic engineer with General Machine Corp. in Washington, D.C.