The eight-corners rule is a rule applied by courts to determine whether an insurance company (insurer) has a duty to defend a claim made against its insured policyholder (insured). The eight-corners rule provides that the duty to defend is determined by comparing the “four corners” of the plaintiff’s pleading (lawsuit) with the “four corners” of the liability insurance policy.

In applying the eight-corners rule, courts generally do not consider facts or evidence from outside the four corners of each of these documents and take the plaintiff’s factual allegations in the pleading as true for purposes of determining whether the insurer has a duty to defend.

But some courts have held that outside or extrinsic evidence may be considered if it demonstrates collusion or fraud between the plaintiff and the insured for the purpose of invoking an insurer’s duty to defend.

Courts generally apply the eight-corners rule liberally and resolve any doubts in favor of the insured by finding the insurer has a duty to defend the insured against the claim(s).

In West Virginia, the eight-corners rule is utilized to determine whether an insurance company has an obligation to defend its policyholder against a claim. This rule involves a comparison of the lawsuit's allegations (the 'four corners' of the plaintiff's pleading) with the terms of the insurance policy (the 'four corners' of the policy). West Virginia courts adhere to this rule by focusing solely on the content within these documents, without considering external facts or evidence, and assume the plaintiff's allegations to be true when deciding on the insurer's duty to defend. While the rule is applied strictly, there are exceptions where extrinsic evidence may be considered, particularly in cases of suspected collusion or fraud aimed at triggering the insurer's duty to defend. Courts in West Virginia tend to interpret the rule in a manner that favors the insured, meaning that if there is any ambiguity or doubt, they are likely to rule that the insurer has a duty to defend the claim.