FRESNO, Calif. >> When a 23-year-old Fresno woman fatally shot her two toddlers and a cousin, critically wounded her husband then turned the gun on herself last Sunday, investigators immediately suspected methamphetamine abuse in what otherwise was inexplicable carnage. It turned out the mother had videotaped herself smoking meth hours before the shooting.

In family photos, the children are adorable, the mother pretty. They lived in a large apartment complex near a freeway with neatly clipped lawns and mature trees. The father was recently laid off from a packing house job.

"When you get this type of tragedy, it’s not a surprise that drugs were involved," said Lt. Mark Salazar, the Fresno Police Department’s homicide commander. "Meth has been a factor in other violent crimes."

A Bakersfield mother was sentenced Tuesday for stabbing her newborn while in a meth rage. An Oklahoma woman drowned her baby in a washing machine in November. A New Mexico woman claiming to be God stabbed her son with a screwdriver last month, saying, "God wants him dead."

"Once people who are on meth become psychotic, they are very dangerous," said Dr. Alex Stalcup, who treated Haight Ashbury heroin users in the 1960s, but now researches meth and works with addicts in the San Francisco Bay Area suburbs. "They’re completely bonkers; they’re nuts. We’re talking about very extreme alterations of normal brain function. Once someone becomes triggered to violence, there aren’t any limits or boundaries."

The Central Valley of California is a hub of the nation’s methamphetamine distribution network, making extremely pure forms of the drug easily available locally. And law enforcement officials say widespread meth abuse is believed to be driving much of the crime in the vast farming region.

Chronic use of the harsh chemical compound known as speed or crank can lead to psychosis, which includes hearing voices and experiencing hallucinations. The stimulant effect of meth is up to 50 times longer than cocaine, experts say, so users stay awake for days on end, impairing cognitive function and contributing to extreme paranoia.

"Your children and your spouse become your worst enemy, and you truly believe they are after you," said Bob Pennal, a recently retired meth investigator from the California Bureau of Narcotic Enforcement.

Methamphetamine originally took root in California’s agricultural heartland in the late 1980s and early 1990s as a poor man’s cocaine. Its use initially creates feelings of euphoria and invincibility, but experts say repeated abuse can alter brain chemistry and sometimes cause schizophrenia-like behavior.

Meth’s availability and its potential for abuse combine to create the biggest drug threat in the Central Valley, according to a new report from the U.S. Department of Justice’s Drug Intelligence Center. From 2009 to 2010 methamphetamine busts in the Central Valley more than tripled to 1,094 kilograms, or more than 2,400 pounds, the report says.

Large tracts of farmland with isolated outbuildings are an ideal place to avoid detection, which is why the region is home to nearly all of the nation’s "super labs," controlled by Mexican drug trafficking organizations, said John Donnelly, resident agent in charge of the U.S. Drug Enforcement Administration office in Fresno.

"They have the potential to make 150 pounds per (each) cook," he said. "There are more super labs in California than anywhere else. Every week another office calls us — St. Paul, Dayton, Kansas, Texas — and says, ‘We’ve got a meth case here’ and they say the suspects are from Turlock or Visalia. We’re slinging it all over the country from here."

Last month, a drug task force working in four central California counties busted 24 alleged members of the Mexican drug cartel La Familia Michoacana with 14 pounds of powdered meth, 30 gallons of meth solution, 17 guns, $110,000 in cash and a fleet of vehicles with sophisticated hidden compartments for smuggling.

Most law enforcement agencies don’t keep statistics on how many homicides, burglaries and thefts are meth-related, but those responding to the National Drug Intelligence Center’s 2011 survey said the drug is the top contributor to violent crimes and thefts.

"It drives more crime than other drugs do. Meth is in its own category, because it’s so much more addictive than other drugs," said Fresno County Sheriff Margaret Mims.

Across the valley, meth addicts steal any metal they can resell — agricultural plumbing, copper wiring, lawn sprinklers.

"We lose five to 10 manhole covers a week," said Ceres Police Chief Art de Werk, who said a woman was injured recently when she fell into an unprotected drain in a shopping center. "Meth is the poor man’s drug and frankly the Central Valley is an impoverished geographic area."

Authorities say the science involved in creating the chemical compound continues to evolve, including an easier recipe called "Shake and Bake" that is available on the Internet. Last month, an Oklahoma woman was arrested as she walked around a WalMart store — for six hours before she was noticed — mixing ingredients for Shake and Bake.

In one of the recent attacks by meth users, Aubrey Ragina Mailloux received a nine- month sentence in Bakersfield Tuesday for stabbing her 6-week-old infant in the back and cutting her along her abdomen, jaw and neck during a binge. The baby survived.

"It’s not illegal because we don’t want people to feel better. It’s illegal because it makes good people do crazy things," said Mailloux’s defense attorney, Mark Anthony Raimondo.

In Oklahoma, authorities charged Lyndsey Fiddler with second-degree manslaughter after an aunt found her infant daughter in a washing machine thudding off balance in the spin cycle. The aunt told authorities that Fiddler had been up for three days using meth.

In Albuquerque, N.M., last month Liehsa Henderson, high on meth, claimed to be God and told police God wanted her son to die after allegedly stabbing him in the neck with a screwdriver. The boy survived.

Last Sunday, Fresno police found Aide Mendez dead on the bathroom floor of her home. Her children — 17-month-old Aliyah Echevarria and Isaiah Echevarria, 3 — were in the bathtub. Mendez’s cousin was dead in the kitchen. She had shot each in the head. The children’s father remains hospitalized with stabbing and gunshot wounds.

Police recovered 10 grams of meth, $8,000 and scales — and the iPad the young mother used to videotape herself smoking meth.

"If she had been on it for any length of time, well it deteriorates your brain and central nervous system," said Sue Webber-Brown, a former DA investigator in Butte County who now advocates nationally for children in drug cases. "If you are already depressed or feel like a loser mom and you don’t have a support system and there is no hope, the meth just fuels that."