While there are a few notable exceptions to this general portrait, many couples (no matter what gender) tend to follow a similar pattern.  Two people meet and feel a strong attraction, or they are related and have established an intimate familiarity with each other that allows them to share fantasies—even violent ones.  Typically one is dominant, and that one seduces the other into sharing his or her fantasy, and then into acting it out.  If they succeed, they get bolder, with the dominant one feeling arrogant and alive, and the submissive one often experiencing some guilt, but reluctant to withdraw.  However, he or she is often afraid of the dominant one, so will continue to go along.

The urge to commit another crime becomes compulsive for the dominant partner.  In the case of two equally dominant partners—more rare but it happens—they egg each other on.  If either feels unsatisfied, that one may go off and commit other crimes on his or her own.  With a dominant/submissive couple, the dominant one determines what they will do next.  As they escalate, the submissive one (who also may be passive-aggressive) will either get out of the situation, undermine the plan or talk to the authorities (or tell someone else that will go report it).  In any event, this person will attempt to end the crimes.  He or she has had enough, either because of safety fears or because the guilt has become a burden.

If both are arrested, the submissive usually will attempt to save himself by turning on the dominant partner and blaming him for the most serious crimes.  At first the dominant one may protect the weaker one, but generally he turns on the other one and implicates him or her.

Inevitably, they end up estranged, with the dominant using whatever leverage he can get from his association with the submissive partner.

Agnes (left), Andras (center) and Tunde Pandy (AP/Wide World)

A typical case was a father-daughter team in Brussels, Belgium, who were convicted of multiple counts of murder in 2002. The father, Andras Pandy, brutalized the daughter, Agnes, including raping her since she was 13.  Out of fear, she was his accomplice for three years, helping him to kill and get rid of five of the six victims that she knew about until she finally confessed to the police.

Andras Pandy was a Hungarian-born priest, but he had raped his daughter and two stepdaughters.  Agnes told authorities about six relatives who were killed—Pandy's first two wives and four of his children and step-children—but the body parts and sets of teeth pulled from the basement and refrigerators on one of his properties were tested for DNA and proved to belong to other people.  In the end, authorities suspected Pandy in the deaths of 13 people, some of them children.  According to Agnes some had been shot and others  bludgeoned to death with a sledgehammer.  She and Pandy hacked the corpses into pieces and wrapped them in plastic.  Some were dumped outside the home, while others were immersed in an acidic drain cleaner called Cleanest, which could dissolve meat from bones and then dissolve the bones themselves. 

Although Pandy denounced the investigation as a witch-hunt without physical evidence, the prosecutor described him as a man who wanted to be in control of those who knew about his incestuous activities.  Mostly that meant killing them.  He claimed that the missing relatives were still alive.  He was in touch with them "through angels."

Mugshot of Agnes Pandy & recent photo of Andras Pandy (AP)

At the conclusion of his trial in 2002, Andras Pandy was convicted on six counts of first-degree murder and three counts of rape, getting life in prison, while Agnes, 44, got 21 years on five counts for her participation.

Agnes claimed that she was equally a victim.  "I had no way out," she said.  "I was completely in his grip."  She was unsparing in her details of Pandy's brutalization.

Agnes was a submissive person who accommodated a killer for three years and who finally turned on him.  While she may not have initiated the crimes, she certainly participated and did nothing on five separate occasions to report her father.  She went along. 

In fact, numerous teams are formed among those who are related by blood or marriage, cementing an intimacy that fully exploits the relationship.