Joan and John were married in 1972. Until 1999 her regular pap smears showed no presence of Human Papillomavirus (HPV), a sexually transmitted disease (STD). It was asymptomatic in John, as it is in most men, but can cause cancer in women. In 1999, after Joan learned of John’s infidelity, she had a pap test which showed presence of the disease. The parties divorced. Joan sued John for negligently infecting her. The Supreme Court had previously dismissed a suit between them. In that case Joan claimed John knew he was infected when he had intercourse with Joan. But the Court dismissed the suit because Joan couldn’t prove John knew he was infected.

The negligence claim required the Court to look at other issues. The Court easily concluded that a spouse is entitled to be protected from contracting an STD from the other spouse. However, negligence also requires proof that John actually knew, or in the exercise of reasonable caution, should have known, he was likely to injure Joan. In a negligence claim, the opportunity to gain knowledge is as good as knowledge itself. This "should have known" standard is called "constructive knowledge." Since there was no proof John actually knew he had the disease. Joan raised several arguments to show John he should have known he was infected. These were:

1. Infidelity is a breach of the marriage vows, and if harm flows from it John should pay.
2. If she had known of the infidelity, she would not have consented to sex with John so John should have told her he cheated.
3. STDs are so prevalent, that extramarital sex is an inherently or abnormally dangerous activity so John should have known he would contract an STD and pass it to Joan.

The Supreme Court dismissed the claim. It held that if Joan proved John had constructive knowledge he was infected he could be forced to pay. But, Joan’s arguments about infidelity and the prevalence of STDS would impose strict liability on John. That is she could win without proof any fault on his part, merely because of the marriage. The Court refused to adopt this rule. It did rule, though, that if John had some warning of his own infection, or consciously avoided finding out whether or not he had an STD, he could be liable. The trouble is that because HPV is asymptomatic in men Joan could not prove John had constructive knowledge.

Cheaters beware, however. The Court recognized how destructive STDs are. It indicated a willingness to find constructive knowledge of infection if the errant spouse had any clue as to his/her infected status. Enders v. Enders 2008 VT. 124.