Many negative consequences can result from failures of a range of different products that often lead to property & casualty insurance disputes or product liability legal actions. The products may include consumer or industrial goods. Typically the private user or worker is injured or a business incurs significant financial loss. The injured individual, insurance carrier, attorney(s) or industrial manufacturer and user are all interested to confirm what went wrong - and who is liable. Resolution often depends on engineering analysis.

Engineers that specialize in performing root-cause failure analyses frequently assist insurance representatives or attorneys in these situations. They are known as forensic engineers in a legal action. Generally there are four broad causes for failures:

• Defective design or inadequate instructions
• Defective materials
• Defective manufacturing
• Misuse or abuse by the user

Defective design may include a variety of factors for which the designer is responsible. For example, incorrect specification of a part for both normal and unintended but foreseeable forces and stresses, specifying the wrong material or choosing a physical configuration that is inherently unsafe. Lack of clear instructions and warnings for safe use are sometimes an issue. Too often technically correct decisions by the design engineer are overridden for cost-cutting reasons and compromises are made that produce accidents.

Defective materials can cause premature failures. Normally this is because of inadequate quality control by the material vendor or unclear specifications for quality by the purchaser. Use of poor quality foreign-supplied materials and parts is a reoccurring issue. Forensic engineers that specialize in materials usage can apply an array of laboratory analysis techniques to define the properties of the failed parts and compare them to specified properties. Obtaining an exemplar of the same, specified material and part to illustrate any differences is very useful.

Defective manufacturing can take many forms. Included could be surface defects left by machining or damage during handling that cause early fatigue failure of parts, improper welding practices that degrade material properties, defects due to improper casting procedures, improper case hardening that causes early wear failure or improper heat treatment of the alloy that produces inferior material properties. Most of these issues are due to inadequate quality control or final testing prior to release of the product. The forensic engineer can generally detect them by careful questioning of the responsible parties coupled with personal inspections and/or laboratory analyses of failed components.

Potential misuse or abuse by the user requires a sensitive approach by the investigating engineer. The injured person may have been seriously harmed by the product failure and thus he or she is deserving of compassion. However, that person also may be defensive if he or she had a role in the accident. The forensic engineer must analyze all available information to include the victim's explanation but also other findings. The attorney that initially retained the engineer may or may not like his final conclusions. The engineer's integrity and professionalism demand that he provides truthful, objective input based on all the evidence. The attorney then can designate the engineer as his expert witness (or not), pursue the case further or seek a settlement.

Depending on whom he has as his insured, the insurance representative may also have options when the engineer has concluded his work and found which of the four root-causes applies. One option may be to pursue subrogation against the responsible party.