"Pretending has always been a part of me," Sandusky, who referred to himself as "The Great Pretender," tellingly wrote in his autobiography, "Touched: The Jerry Sandusky Story."
Madoff and Sandusky may have hidden their predilictions well. But even when a loved one poses a clear and present danger to society, relatives don't always intervene effectively.
In documents released in March, it was revealed that Arizona mass shooter Jared Loughner's behavior was so disturbing that his father confiscated his shotgun and disabled his car every night to keep him home in the months leading up to the rampage.
But when the signs are subtle, it's easy to miss them --sometimes it's even desirable from the point of view of the spouse.
Life partners have an investment in seeing one another through rose-colored glasses, Saltz says, especially if they have a child and are deeply invested in the marriage.
"It does take some complicity on the part of the person that doesn't know in order to not know. It's not necessarily conscious complicity," she said.
Brateman says denial absolutely comes into play.
"They may see some of these symptoms and not actually know what they mean," Brateman said. "They say, 'Oh, he/she is agitated' or 'in a bad mood,' but they don't ever imagine that that could mean something."
"In the aftermath of the Patriots' Day horror, we know that we never really knew Tamerlan Tsarnaev," said the Russell family's statement. "Our hearts are sickened by the knowledge of the horror he has inflicted."
Russell, whom her lawyer Amato DeLuca describes as "very distraught," might be dealing with the psychological impact of realizing her life with Tsarnaev was not normal. She may feel robbed of her belief system and sense of self, Brateman says.
Living a dual life is "the ultimate act of betrayal," Brateman says. "It doesn't just defy marriage, it defies humanity."