Metallurgy Expert Witness Advises on Tree Stand Failure that Results in Hunter’s 3-Story Fall

A metallurgy expert witness advises on a case involving an avid bow hunter who regularly used a tree stand in Missouri. He was injured when two ratchet straps failed, causing him and the tree stand to fall about 30 feet to the ground. The straps were replacement straps that had been used for a total of about six weeks. When the stand was not in use, the plaintiff stored it and the straps in his garage.

Question(s) For Expert Witness

1. Were the straps defective?

2. Should the manufacturer have tested the straps?

3. Should it have included warnings?

Expert Witness Response

I conducted material evaluation and failure analysis of two fractured 1″ wide polymer webbing ratchet straps. The two submitted fractured ratchet straps with end hooks were reportedly utilized to affix the plaintiff’s hang-on tree stand.

To a reasonable degree of engineering probability, I conclude that the replacement tree stand ratchet straps are defective as manufactured. The design drawings and documents produced to date by the defendant are inadequate to determine if the subject ratchet straps contain design defects as well as manufacturing defects. No documents identifying the specific polymer chemistry for the webbing has been produced. This PP webbing should contain antioxidants and be UV stabilized for typical weather exposure for a tree stand for 5 to 10 years as a minimum. Without an expiration date, the exposure degradation protection of the webbing material may need to exceed this time frame. Defendant and its manufacturing companies in China do not even test the strap webbing to determine its loss of strength as it weathers in a normal hunting environment.

The defective subject ratchet straps had severely reduced breaking strengths as a result of weathering over only a short usage period of 22 to 23 weeks over 3 years. There is no written expiration date on the ratchet straps so they could conceivably be available to a consumer for even longer periods of time. Without any written inspection criteria supplied to the user of these ratchet straps, strap users cannot determine if the straps are safe to use in their tree stand. Environmental degradation of polymers requires specific inspections to determine the damage to polymer filaments and the weakening of the webbing. These two companies gave their strap users no inspection criteria. These subject replacement straps contain inadequate and defective material engineering design features, guarding, or warnings on how to prevent the use of these straps if they are in a dangerous, weakened condition. As these straps are the sole attaching device for a hang-on tree stand, they are the device that must be designed to be the most failure resistant component of a hang-on tree stand, not the most likely to fail.

The expert is an engineer and metallurgist experienced in failure analysis.