Personal injuries are extremely common, and yet, almost always unexpected. They can manifest in the most surprising ways and under such varied circumstances. Some of the most common types of personal injury claims that we deal with as an engineering firm result from product liability, which includes faulty machinery and malfunctioning household items; workplace injuries which can range from minor cuts and bruises to severe accidents involving heavy machinery or exposure to hazardous materials; and slip and fall accidents caused by poorly maintained walkways, uneven surfaces, as well as building code violations.
There are, of course, other categories of personal injuries which as engineers we do not investigate, including medical malpractice, animal bites, defamation or emotional distress. All the same, OCI Group has been involved in a large number of diverse and complex investigations involving personal injury. claims. For the purpose of this article, I am going to discuss some examples focusing on product liability.
In this incident, a disabled person was attempting to cross the street in his electric wheelchair, when suddenly he lost control and the wheelchair flipped over. The person was thrown from the wheelchair which then landed on top of him, causing additional injury as it weighed in excess of 100 kilograms. When we examined the wheelchair, we found nothing wrong with the wheels, brakes or battery, but, with the joystick. The joystick controlling the movement of the wheelchair was not secured by a set screw, which would prevent it from coming loose. As a result, it simply separated from the shaft, making the device uncontrollable. We concluded that the accident was caused by a manufacturing design deficiency. Had the joystick been properly secured in place, the accident would not have happened. The manufacturer of the wheelchair was ultimately held accountable for the accident.
This case, which also involved a chair, occurred in a travel agency waiting room. One day, a father was sitting in the incident chair, holding his child, when the chair collapsed and the child fell headfirst onto the floor, sustaining injuries. We were requested to investigate and provide an independent engineering opinion on the most probable cause of the accident. Our complex investigation revealed that the chairs, which were made overseas, exhibited poorly welded joints. These substandard welds, having large undesirable porosities, diminished the load carrying capabilities of the chairs. As a result of the investigation, the plaintiff received compensation – not from the manufacturer, who was based in China – but from the national distributor. Additionally, 800 similar chairs across Canada had to be taken out of service.
In an upsetting and unusual case, a fragment from a ruptured toilet bowl severed the artery of a young girl who was sitting on the toilet at the time of the incident. Luckily, she survived but the question of how this happened remained. Toilets are made of vitreous china, a type of ceramic material made from a mixture of clay, kaolin, silica, feldspar, and water. The liquid clay is poured into a mold and left to set for a specific time. After the toilet pieces are shaped, they are dried in an oven to remove excess moisture. Any residual porosity left in the material will act as a stress concentrator and eventually will cause the component to break, which is exactly what happened to the toilet in this instance. Our investigation, including microscopy examination and porosity measurements, found that the incident toilet was substandard and that it exhibited excessive porosity. The internal residual stresses can remain locked in for extended periods of time, and this would explain why the accident occurred years after the toilet was installed. As a result of our investigation, the manufacturer was held liable for the accident.
In this tragic accident, a roofer was scaling a multi-position ladder when it collapsed, causing him to fall and paralyzing him from the waist down as a result of his injuries. The ladder was preserved and subjected to a joint destructive examination involving multiple parties: the manufacturer of the ladder, the manufacturer of the hinges, the distributor, the seller, and the plaintiff. The failure occurred at an aluminum hinge, which had fractured completely. Laboratory examination by scanning electron microscopy revealed the cast aluminum hinge exhibited undesirable porosity which resulted in diminishing load-carrying capabilities. The manufacturer of the ladder hinge was able to positively determine the foundry where that specific hinge was cast, and the foundry was held liable.
A dental lamp is a specialized lighting fixture used in dental practices to provide focused, adjustable, and bright illumination during procedures. This lamp is typically mounted above the dental chair and is adjustable, having flexible arms, allowing the light to be directed precisely where it’s needed. The arms of the lamp are connected through hinges to provide versatility in positioning and movement. In this instance, during a routine checkup, one of the mounting brackets for a hinge broke and the lamp fell onto the patient’s head, causing severe injuries. The complete fracture of the lamp arm occurred at one of the threaded connections of the bracket. Further examination of the fracture surface under a microscope revealed the presence of features referred to as beach marks, which are always associated with a degradation mechanism known as fatigue. Fatigue is a progressive and localized damage that occurs in a material when it is subjected to repeated or fluctuating stresses over time. In this case, the fatigue was caused by an improperly torqued mounting screw, which created a stress concentrator where the failure was initiated. The accident was attributed to a maintenance issue, and both the contractor and the dental practice were held liable.
In this fatal accident, a young driver lost control of his vehicle and hit two cyclists head-on in the oncoming lane, one of whom died instantly. The blame for the accident was cast on a fractured tie rod. The question brought to us: Was the fractured tie rod the problem? Was it corroded, fatigued, defective? Did it fail first, leading the driver to lose control of the vehicle? Our investigation included metallurgical evaluation and scanning electron microscopy of the fracture surface and revealed that the tie rod failed by ductile overload, or, in other terms, it failed as intended. This sounds bizarre, I know. But it is a term used in materials engineering, and it means that the material failed after its ultimate strength (the maximum stress a material can withstand before failure) was exceeded and not due to a defect. The tie rod condition was not the problem; it fractured as a result of the impact. Microscopic examination of the fracture surface revealed the presence of features called dimples, which are always associated with ductile overload fracture. Metallurgical evaluation of the microstructures did not reveal any gross metallurgical deficiency in the material. As a result, we were able to conclude that the tie rod did not contribute to the accident.
Personal injuries can significantly impact an individual’s life. Whether due to an accident, negligence, or intentional harm, they can lead to physical pain, emotional suffering, financial burdens, and long-term disability. Personal injury claims seek to compensate the injured person and hold negligent parties accountable. This quest to find fault often leads to finger-pointing. One party alleges a manufacturing defect, another tries to blame it on user error, and still another asserts that the issue is clearly improper installation or lack of maintenance or a design deficiency or any number of other causes. The point being, that there is no shortage of opinions, and plenty of blame to go around. But as this article hopefully illustrates, determining the true cause requires a thorough understanding of how systems, products, and materials are constructed and how they behave under different conditions. It’s critical that conclusions are based on thorough, scientific evaluation rather than assumptions or mere surface level observations. Personal injury claims are not just about establishing blame but about uncovering the truth with precision and clarity, ultimately leading to improved safety practices and better lives.
