The federal government's increasingly convoluted marijuana policy is on trial in California, where a U.S. district court is considering a challenge to the 44-year-old law that lists pot alongside heroin and ecstasy as one of the most dangerous and harshly regulated illicit drugs.

Congress and the Nixon administration first slapped marijuana with a Schedule I designation as part of the Controlled Substances Act of 1970. Placement in this group requires that a drug, chemical or controlled substance "has no currently accepted medical use and a high potential for abuse."

This new challenge, launched by a group of defendants on trial for illegally growing marijuana, argues that pot no longer fits that classification and, in so doing, questions the constitutionality of the decades-old law.

U.S. District Judge Kimberly Mueller allowed the defendants to make their case in an unusual pretrial hearing, which, according to the Los Angeles Times, included expert testimony and "thousands of pages of briefs, exhibits and declarations." The five-day hearing featured pointed arguments from federal prosecutors, who had to make the case that marijuana still belongs in the Schedule I group despite overwhelming new evidence that the drug has great medicinal value and does not cause serious addiction.

U.S. v. Science: Assistant U.S. Attorney Gregory Broderick, writing on behalf of the federal government, argued that "most mainstream physicians agree that marijuana is a dangerous drug" and that there remains "some dispute among doctors as to whether marijuana is medicine."

Ironically, Broderick and his colleagues filed their brief just weeks after the Obama administration and the new Republican-controlled House and Senate signed off on a spending bill that explicitly forbids the Department of Justice from using federal funds to interfere with state-approved medicinal marijuana operations.

David Goldman/AP

But more important here is the large and growing stack of research, much of it presented by the defendants in California, that shows marijuana is not just useful in a medical setting, but could provide necessary comfort to patients with chronic ailments ranging from epilepsy and glaucoma to post-traumatic stress disorder.

And lest this become a question of competing studies, there is the fact that no one has ever died of a marijuana overdose. Heroin, also a Schedule I drug, killed 5,925 people in the U.S. in 2012 alone. Cocaine, which is prosecuted as a less dangerous "Schedule II" substance, becomes lethal at 10-12 times its "effective dose." As the Huffington Post reports, scientists believe you'd need to smoke between 20,000 and 40,000 joints in one sitting to kill yourself with marijuana. No one ever has.

Experience in Colorado and Washington state, and any of the 23 states (plus the District of Columbia) that have legalized pot for medicinal use only, proves that the marijuana smoke is no worse for your lungs than cigarettes and no more addictive than a cup of coffee. Neither nicotine or caffeine are controlled substances.

The court's decision: The L.A. Times reports that Judge Mueller isn't expected to make a ruling until "later this year." If she finds in favor of the defendants, prosecutors are expected to appeal to the 9th Circuit Court of Appeals, which has jurisdiction over nine western states in addition to Guam and the Northern Mariana Islands.

In the unlikely event both courts agree with the defendants (whose case features some pretty complex arguments about constitutionally guaranteed equal protection and states' rights), the next stop would be Washington, D.C., and the U.S. Supreme Court.