IStock Photo 8363437 © Matjaz Boncina

On December 24, 2002, Laci Peterson, who was 27 years old and eight months pregnant, was reported missing. She and her husband Scott Peterson lived in Modesto, California.

On January 24, 2003, ABC News reported that Peterson had been having an affair with Amber Frey, who would later testify for the prosecution at trial. On April 13, 2003, a male fetus was found along the banks of San Francisco Bay. The site was due north of the Berkeley Marina, the spot at which Peterson had been boating the day his wife disappeared. The following day, part of a female body washed ashore in the same area. On April 19, 2003, the Los Angeles Times reported that the partial torso was that of Laci Peterson and the fetus was her unborn child. Forensic searches were conducted in the Peterson house as well as Peterson’s truck, warehouse, and boat. A single strand of human hair believed to be Laci’s was discovered on a pair of pliers in Peterson’s boat.

On November 12, 2004, a jury convicted Peterson of first-degree murder in the death of Laci Peterson and second-degree murder in the death of their unborn child. Stories like this make front-page headlines, but are they as uncommon as one might think? Dr. Diana Cheng and Dr. Isabelle Horon undertook a study to discover the most likely cause of death among pregnant women in Maryland. Their findings, which were published in the Journal of the American Medical Association (JAMA), revealed that the leading cause of death among 247 women studied, over a period from 1993 to 1998, was homicide. This accounted for approximately 20% of the cases.

The odds seem to indicate that these cases are not isolated incidents. According to 2008 data from the FBI, the odds a victim of a solved murder was in an intimate relationship with the murderer are 1 in 5.94. Murders by a spouse make up a large proportion of these cases, and much more often than not the murderer is the husband. While the odds the victim of a solved murder was the murder’s wife are 1 in 13.71, the odds the victim was the murderer’s husband are only 1 in 66.49. The killing of one’s wife has been so prevalent throughout the centuries that The Merriam-Webster Online Dictionary traces the word uxoricide—murder of a wife by her husband—back to 1733.

While the Bureau of Justice Statistics reports that the number of intimate homicides (that is, those committed by a spouse, ex-spouse, or lover) has declined since 1976, most of the decline is due to fewer male victims killed by intimates. In recent years, according to the agency, one third of female murder victims died at the hands of an intimate, while only about 3% of men met the same fate.

Why is marriage often a path to murder instead of a stroll hand-in-hand? According to Psychology Today, the most popular theory is that a confluence of male psychological traits—all stemming from jealousy or possessiveness—triggers lethal violence, which explains why the murder of one’s wife is rare relative to other violent domestic disputes. A second theory is that the murder of one’s wife is unintended, that it is the shocking result of a violent episode that has spiraled out of control.

In some cases the motivation seems to be material gain, or the desire to start a new life, unencumbered by a spouse. In others, it’s the apparent belief that a list of grievances and problems can be solved with one violent act. Take the case of Jamie and Harold Stonier. According to an account in the Boston Globe, at his 2005 trial Harold Stonier gave a number of reasons for trying to hire a hit man to murder his wife—from his claims that she was a bad mother to his complaints about her spending.

An article published by ThirdAge.com about marital status and wellbeing claims marriage can either be the “fairytale you dreamed of all your life, or it can be an eternity of trouble and strife.” Judging by the odds, it can also lead to homicide.