What if the insured lied about a heart attack?
If he dies within 2 years (or in some states, three years) of the date the policy was issued -- and the insurer can prove the applicant knew he had had a heart attack -- the life insurer would deny coverage. His statement that he did not have a heart attack on the application is regarded as a "representation" and not a warranty. If he had what is known as a "silent" heart attack -- which was only detected on autopsy -- the insurer would pay the claim.
If he dies after 2 years -- unless the insurer instituted a legal action to "rescind" the policy within 2 years -- the policy is essentially "uncontestable". That means the insurer would have to pay the claim even if the insured had lied as blatantly as Bill Clinton lied about Monica Lewinsky, at least in almost all cases. (There is an exception for misstatements of age, and in some states, if an "imposter" took the physical for the insured.)