WASHINGTON, D.C.: The Washington Supreme Court ruled unanimously that Amazon.com must face lawsuits from families whose relatives died by suicide after purchasing sodium nitrite from third-party sellers on the retailer's website.

All nine justices overturned a lower appellate court ruling that had found the families could not pursue negligence claims because suicide was a superseding cause of death.

Writing for the court, Justice G. Helen Whitener said Amazon owed customers a duty of reasonable care and must avoid exposing them to "harm from the foreseeable conduct of a third party."

She said it should be up to a jury to determine whether suicide was a foreseeable result of Amazon's alleged failure to meet that duty.

Twenty-eight families have filed lawsuits accusing Amazon of allowing unrestricted sales of sodium nitrite despite knowing for years about its connection to suicides. The families allege that the chemical was sold alongside other items that could assist in suicides, referring to them collectively as "suicide kits."

They are seeking unspecified damages under Washington state product liability law for the deaths of their relatives.

The decision on February 19 addressed appeals brought by four of the families, who said they lost relatives aged 17 to 27 in 2020 and 2021 after they consumed sodium nitrite that was 98 percent or 99.6 percent pure.

Amazon said it disagreed with the ruling but expressed condolences to families affected by suicide.

In a statement, the company said it remains committed to customer safety and noted that highly concentrated sodium nitrite "is not intended for direct consumption, and unfortunately, like many products, it can be misused."

Sodium nitrite is a legal chemical commonly used as a preservative in meat and fish products. It is also used in research laboratories and to treat cyanide poisoning.

The case is part of a broader wave of litigation seeking to hold online marketplaces responsible for products sold by third-party vendors.

"Amazon is one of the world's biggest companies, and shouldn't be profiting from products they know people use to harm themselves," said Carrie Goldberg, a lawyer representing the families.

Amazon said it now prohibits the sale of sodium nitrite with purity levels above 10 percent.