Richard and Nancy Lyon

More than two million marriages are celebrated each year in America. Some last forever. Many don't.

A simple divorce is the solution for the vast majority of couples when wedded bliss loses its fragrance. The country records just under one million divorces every year.

A small percentage of marriages end without the legal niceties. Each year, several thousand intimate relationships in America are terminated by murder.

Roughly one-quarter of all women slain are killenicd by a husband, a boyfriend or an ex, according to government statistics. The proportion is lower for men, but the raw numbers are similar. A groundbreaking study of spousal homicides committed in 1988 found that four in 10 killer spouses were women.

The vast majority are predictably mundane: a drunken argument ending in violence.

Seven in 10 domestic homicides result spontaneously from an argument. Nearly two-thirds of the perpetrators are under the influence of alcohol or drugs.

In these cases, access to a weapon tops off the lethal mix of anger and intoxication, and the criminal justice system is left to mop up mess left behind from a classic passion-of-the-moment killing.

Women who kill their spouse use a gun or a knife in roughly 95 out of 100 cases. Men use those weapons or their fists at a comparable rate.

In most of these instances, a spouse is blinded by rage while committing the deadly act, often later regretted.

But in the margins of those numbers — the exceptions to the statistical rules — are the homicides that often make front page news — cases like those of Scott Peterson, Christian Longo, Pam Smart and Ruth Snyder.

For each of them, a marriage had gone sour, but none considered divorce a viable option.

Why? In a word: money.

Perhaps the targeted spouse is wealthy and the conniving spouse cannot bear the thought of a life of freedom fettered with bills — alimony, child support, lawyer fees, credit card debt, even mortgage payments for a former home.

And then there is the classic motive: a big life insurance payday.

These pathological spouses make what they believe are reasoned decisions to save — or make — money by murder. Some do their own work, while others employ killers for the task.

Most of these murders are carried out with the usual implements of death — guns, knives, fists or various blunt objects.

But murder comes in many forms, and a fraction of these premeditated killers choose an ancient method: poison.