"This is a historic step forward for Californians with terminal illnesses who have been looking to the legislature for the option to determine the quality of their final days of life based on their own personal beliefs," said Senator Bill Monning, one of the backers of the bill approved by the state assembly on Wednesday.
The measure, approved by 43 votes against 34, is expected to be adopted by the state senate this week.
Euthanasia, or assisted suicide, has long been a controversial issue in the United States, with Montana, New Mexico, Oregon, Vermont and Washington the only states to have approved it so far.
The topic was brought to the forefront in California by the case of Brittany Maynard, a 29-year-old with a brain tumor who moved from San Francisco to Oregon and took her own life last November.
"Her case brought the story to the public in a way that hadn't been done before," said Monica Schmalenberger, an aid to California Senator Lois Wolk, a supporter of the euthanasia bill.
Another woman suffering from leukemia is suing the state of California demanding the right for doctors to assist terminally ill patients end their lives.
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