Penal Code section 422 makes it a crime to "willfully threaten to commit a crime which will result in death or great bodily injury to another person, with the specific intent that the statement, made verbally, in writing, or by means of an electronic communication device, is to be taken as a threat, even if there is no intent of actually carrying it out, which, on its face and under the circumstances in which it is made, is so unequivocal, unconditional, immediate, and specific as to convey to the person threatened, a gravity of purpose and an immediate prospect of execution of the threat, and thereby causes that person reasonably to be in sustained fear for his or her own safety or for his or her immediate family's safety . . . ." To prove a violation of section 422, the prosecution was required to establish: "(1) that the defendant 'willfully threatened to commit a crime which will result in death or great bodily injury to another person,' (2) that the defendant made the threat 'with the specific intent that the statement . . . be taken as a threat, even if there is no intent of actually carrying it out,' (3) that the threat--which may be 'made verbally, in writing, or by means of an electronic communication device'--was 'on its face and under the circumstances in which it was made, . . . so unequivocal, unconditional, immediate, and specific as to convey to the person threatened, a gravity of purpose and an immediate prospect of execution of the threat,' (4) that the threat actually caused the person threatened 'to be in sustained fear for his or her own safety or for his or her immediate family's safety,' and (5) that the threatened person's fear was 'reasonable' under the circumstances." (People v. Toledo (2001) 26 Cal.4th 221, 227-228 (Toledo); 422.) Both the language and all the surrounding circumstances must be examined to determine if a threat falls within section 422. (People v. Gaut, 95 Cal.App.4th at p. 1431.) In reviewing a judgment for the sufficiency of the evidence, a court must review the evidence in the light most favorable to the judgment, to determine if there is substantial evidence from which any rational trier of fact could find each element of the crime beyond a reasonable doubt. (People v. Ceja (1993) 4 Cal.4th 1134, 1138; People v. Bloom (1989) 48 Cal.3d 1194, 1208.) In making this determination, the reviewing court must presume every fact in support of the judgment that the jury could reasonable have deduced from the evidence. (People v. Rayford (1994) 9 Cal.4th 1, 23; People v. Ochoa (1993) 6 Cal.4th 1199, 1206 (Ochoa).) Moreover, the "uncorroborated testimony of a single witness is sufficient to sustain a conviction, unless the testimony is physically impossible or inherently improbable." (People v. Scott (1978) 21 Cal.3d 284, 296; People v. Elwood (1988) 199 Cal.App.3d 1365, 1372.) The reviewing court must afford due deference to the fact finder and cannot substitute its evaluation of a witness's credibility for that of the fact finder. (Ochoa, supra, 6 Cal.4th at p. 1206.) In People v. Garrett (1994) 30 Cal.App.4th 962, the defendant was charged with threatening his wife with great bodily injury, pursuant to Penal Code section 422. The court held, over the defendant's claim of undue prejudice, that it was proper to introduce evidence that the defendant's wife knew he had a prior manslaughter conviction. The court noted that section 422 requires the prosecution to show the victim reasonably was in sustained fear for her safety. (Garrett, supra, at pp. 967-968.)