California's gun-control laws are among the nation's most stringent, yet they couldn't have prevented Philip Marshall - dependent on drugs, diagnosed with a mental disorder and with a history of domestic legal troubles - from buying the handgun he used to kill his two children and himself earlier this year, according to various authorities on the topic.
The reasons are myriad, but relate to the thresholds required to report criminal histories and mental conditions.
"Right now, the only thing that's going to show up is if you're declared unfit by the courts or if you've committed a crime and been convicted," said Sgt. Chris Hewitt, Calaveras County Sheriff's Office spokesman.
Marshall, 54, bought the Glock Model 19 9mm semiautomatic handgun used to kill his son Alex, 17, daughter Macaila, 14, and himself in October 2011 in Turlock.
That was six years after the airline where he worked as a pilot dismissed him for bouts with mania and depression, and three years after a series of domestic disputes with his estranged wife that at one point led to a court order to keep away from her.
The ammunition used was purchased at a Sonora sporting goods store days before the shootings, which were reported Feb. 3 but are believed to have occurred between Jan. 31 and Feb. 2 at the family's Forest Meadows home.
To purchase a handgun in California, state law requires a 10-day waiting period, possession of a handgun safety certificate after a test given by a Department of Justice-certified instructor, and completion of a safety demonstration with the gun to be purchased.
It also requires a background check of criminal and mental-health history.
The law is being considered as a model for federal legislation requiring universal background checks, one of the most popular gun control reforms proposed following the Sandy Hook Elementary School massacre of 20 students and six adults in December in Newtown, Conn.
Information that would disqualify a candidate is logged into databases used by the state Department of Justice in conducting the background checks.
Yet the background check has its limits, as evidenced by the Marshall shootings.
In fact, California's checks lead to a denial rate of about 1 percent, whereas the national average is 0.6 percent, according to federal Bureau of Justice statistics.
Department of Justice spokeswoman Michelle Gregory said disqualification for a history of a mental condition requires specific triggers.
A licensed psychotherapist would have to report specific threats of violence made by a patient to show up during a background check, she said.
Appointment of a conservator or an involuntary commitment to a mental hospital are also flagged, Gregory said.
"Disqualifications are extremely narrow. The number of people who have diagnoses in their histories is very large," said Frank Zimring, a University of California, Berkeley, law professor who studies gun control. "It's only the most extreme of mental health cases that current law would disqualify."
In Marshall's case, he was diagnosed as bipolar and dismissed and grounded as a pilot by United Airlines in 2006 as a result of alternating periods of depression and mania, according to the Sheriff's Office.
"A diagnosis is different from commitment or a straight-out threat," Gregory said.
For example, Jared Loughner, convicted of shooting and killing six people and injuring 12 others including then-Congresswoman Gabby Giffords in January 2011 in Tucson, Ariz., was a diagnosed as schizophrenic and his college suspended him pending a mental health evaluation. Yet Loughner too passed a background check.
"Nobody would call the mental health check anything other than a work in progress," Zimring said. "(Enhancement) has to be talking about making much broader assumptions about the suitability of excluding people with a history of mental problems from gun ownership and that's a huge leap."
A federal National Instant Criminal Background Check System was implemented in 2007, following a mass shooting at Virginia Tech University. But only 27 states, including California, either allow or require reporting of pertinent mental health information to the database.
Any person who is "addicted to the use of narcotics" is prohibited from obtaining a weapon, according to state and federal law.
The problem is, there is little information available to law enforcement to determine who those people are.
A criminal conviction related to narcotics use or possession is the primary way of flagging applicants for that prohibition, Gregory said.
Marshall had no such conviction.
From mid-2012 through January 2013, however, Marshall frequented a local clinic seeking additional medications for chronic back pain, according to the Sheriff's Office's investigation. As a result, the clinic's doctors made him sign a pain medication contract, pledging he would take the pills as prescribed and not seek medication from other doctors.
Medical records indicated he had been referred to a psychiatrist but "it is unknown whether he ever attended this appointment," the Sheriff's Office said.
A toxicology screen, following the murder-suicide, showed the painkillers hydrocodone and morphine in Marshall's blood as well as hydroxybupropion, a derivative of the antidepressant bupropion, commonly sold as Wellbutrin.
Investigators consulted a doctor and FDA research showing bupropion and hydrocodone taken in combination "can have adverse reactions in regards to mental health." Any abrupt changes in usage "could result in suicide, hostility, or psychosis," their report found.
Someone with a restraining order, or similar court order, against them cannot possess a weapon.
Marshall violated an emergency protective order against him served during a divorce proceeding with estranged wife Sean Plummer in December 2008, according to the Sheriff's Office.
However, no charges were filed against him in that case nor after an arrest for allegedly slapping Plummer's sister, Erin Chamberlain, at her Murphys home the same month.
A conviction for violating a protection order typically leads to a firearm prohibition for the next 10 years, according to a Department of Justice information sheet. Since Marshall was never convicted, however, he was not excluded.
The Newtown shootings prompted a slew of proposed legislation in California to tighten gun controls. Ideas include bans on certain weapons, taxes specific to ammunition, limits on the amount of ammo that can be purchased and extending background checks to include those seeking to buy ammunition, not just firearms.
The latter is included in Senate Bill 53, written by Sen. Kevin De Leon, D-Los Angeles. It would require a permit, good for five years, to buy ammo beginning in 2017. A background check that can take up to 30 days is proposed prior to issuance of the permit.
Marshall purchased the ammunition used to kill his children and himself on Jan. 27, less than a week before the crimes were committed, according to detectives.