Legal Definitions - major–minor fault rule

The major–minor fault rule is a historical principle in maritime law that applied to collisions between vessels. This rule stated that if the fault of one vessel was so overwhelmingly clear and substantial that it fully explained the cause of an accident, then any minor or questionable fault on the part of the other vessel would be disregarded. In such a scenario, the vessel with the minor fault would be presumed not to have contributed to the collision.

Essentially, if one vessel's negligence was undeniably the primary and sufficient cause of a collision, any lesser, secondary, or technical fault by the other vessel would not be considered a contributing factor to the accident. This rule aimed to simplify liability determinations when one party's error was clearly dominant.

It is important to note that this rule has largely become obsolete in modern maritime law. Most jurisdictions now apply principles of comparative fault, which allow courts to apportion responsibility for damages based on each party's precise degree of fault, rather than assigning all blame to one party or disregarding minor faults.

Here are some examples illustrating how the major–minor fault rule would have applied:

• Imagine a large cargo ship, due to a severe navigational error by its crew, veers sharply out of its designated shipping lane and collides with a small fishing trawler. The trawler might have had a slightly less bright stern light than regulations required. Under the major–minor fault rule, the cargo ship's profound navigational error would be considered the "major fault," sufficient to fully explain the collision. The trawler's dim light, while a technical fault, would be deemed a "minor fault" and would not be considered a contributing cause to the accident. The cargo ship would bear full responsibility.

• Consider a scenario where a large passenger ferry, operating at excessive speed in dense fog, crashes into a smaller tugboat. The tugboat's radio might have been momentarily tuned to the wrong channel, causing a slight delay in receiving a warning. In this case, the ferry's reckless speed and disregard for fog protocols would be the "major fault," clearly accounting for the collision. The tugboat's minor radio issue would be overlooked, and the tugboat would not be held responsible for contributing to the accident.

• Suppose a poorly maintained pleasure craft experiences a complete engine failure and drifts uncontrollably into a dock, striking a moored sailboat. The sailboat's mooring lines, while secure, might have been slightly older than recommended for optimal strength. The pleasure craft's catastrophic engine failure due to neglect would be the "major fault" that directly caused the collision. The sailboat's slightly aged mooring lines would be considered a "minor fault" and would not be seen as contributing to the incident, placing full liability on the pleasure craft.