If the beneficiary of a life insurance died before the policy holder do you need a copy of the beneficiary death certificate?

Yes. If there is a contingent beneficiary, the insurance company will need proof that the primary predeceased the principal in order to pay the contingent beneficiary. If there was no contingent beneficiary named the insurance company will pay the proceeds to the principal's estate.
Yes. If there is a contingent beneficiary, the insurance company will need proof that the primary predeceased the principal in order to pay the contingent beneficiary. If there was no contingent beneficiary named the insurance company will pay the proceeds to the principal's estate.