Does a witness need actually see the testator sign the will?

This answer depends on the laws of the state in which the will is executed and/or perhaps in the state where the will is going to be offered for probate. Some states are more lenient than others with regard to execution. In some states like NJ, a will is properly executed if a witness either sees the testator sign the will or hears the testator acknowledge that the signature on the will is his/hers. This permits a testator to sign the will in front of one person then later tell another person that he signed it and that the signature is his/hers. The second witness would sign the will as a witness, but the attestation clause would have to be re-Worded to state that the second witness did not see the actual signing but did hear the testator acknowledge his signature.