California Code, Penal Code - PEN § 139

(a) Except as provided in Sections 71 and 136.1, any person who has been convicted of any felony offense specified in Chapter 3 (commencing with Section 29900) of Division 9 of Title 4 of Part 6 who willfully and maliciously communicates to a witness to, or a victim of, the crime for which the person was convicted, a credible threat to use force or violence upon that person or that person's immediate family, shall be punished by imprisonment in the county jail not exceeding one year or by imprisonment pursuant to subdivision (h) of Section 1170 for two, three, or four years.

(b) Any person who is convicted of violating subdivision (a) who subsequently is convicted of making a credible threat, as defined in subdivision (c), which constitutes a threat against the life of, or a threat to cause great bodily injury to, a person described in subdivision (a), shall be sentenced to consecutive terms of imprisonment as prescribed in Section 1170.13.

(c) As used in this section, “a credible threat” is a threat made with the intent and the apparent ability to carry out the threat so as to cause the target of the threat to reasonably fear for his or her safety or the safety of his or her immediate family.

(d) The present incarceration of the person making the threat shall not be a bar to prosecution under this section.

(e) As used in this section, “malice,” “witness,” and “victim” have the meanings given in Section 136.