Sebastian Telfair's estranged wife claims the NBA star's sister threatened to "kill my kids and cut my face" ... all because she testified against Sebastian in his NYC gun case.
Law enforcement sources tell us ... the LAPD responded to a call last week from Samantha Telfair, who claims Octavia Telfair called her roughly 52 times making various threats ... including a threat to "Slice [her] face and kill [her] children."
Samantha told cops Octavia was furious that Samantha took the stand earlier this month and told prosecutors she had seen Sebastian with multiple weapons, including the gas-operated submachine gun he was allegedly carrying when he was arrested in June 2017.