The panel agreed with a federal judge that the manufacturer had no reason in 2004 to tell police agencies use of the weapon could trigger metabolic acidosis, the Los Angeles Times reported.
In that condition, lactic acid produced during physical exertion accumulates more quickly than the body can expel it and raises raises the risk of a heart attack. But the court ruled there was no evidence in 2004 that Tasering caused metabolic acidosis.
Michael Rosa, 38, died in 2004 after police repeatedly shocked him with electricity from Tasers in Del Rey Oaks, Calif. Police, responding to a report that a "pretty disturbed" man was walking around and yelling, repeatedly fired Tasers at Rosa before putting him into handcuffs, the Times said.
He died shortly thereafter. High levels of methamphetamines were found in his blood, and his death eventually was linked to acidosis, the Times reported.
His parents sued the manufacturer on the grounds the company should have warned of the risk.
The company argued there is no evidence Tasers cause acidosis but began warning about it anyway in 2009.