¶1OPINION OF THE COURT
¶2Appellant, Carol Dillon, was found guilty of murder in the third degree and possession of an instrument of crime following a jury trial in the Court of Common Pleas of Philadelphia County. The trial court denied her post-trial motions and sentenced her to a prison term of not less than three years and no more than six years. Appellant appealed to the Superior Court, which affirmed 386 Pa.Super. 236, 562 A.2d 885. We granted allocatur. We now reverse on the basis of the trial court’s exclusion of evidence presented by appellant as herein set forth.
¶3Appellant was accused of stabbing and killing her husband, James Dillon, in their home on Saturday, June 7, 1986. Appellant admits to the fatal stabbing but asserts that she did so in self-defense after the decedent, who was drunk at the time, attacked her. At trial, appellant testified that the decedent had become violent when drinking and beaten her on numerous occasions (T.T., 11/4/87, pp. 7-8).
¶4*420To support her testimony that the decedent became violent when drinking, appellant attempted to introduce the testimony of her son, Robert Weinert Jr., regarding the decedent’s character for violence when intoxicated. According to the offer of proof, Weinert would have testified that “during the time he visited the home, he and his friends, James Dillon Sr.’s, would get in the basement at which time they would drink and smoke marijuana and inhale it and he would get drunk and mean and vicious.” The trial court refused to admit Weinert’s testimony because it considered the testimony irrelevant and incompetent. The trial court did, however, permit two Commonwealth witnesses to testify on rebuttal that decedent was normal and happy when drinking (T.T., 11/4/87, pp. 100, 113).
¶5In a trial for homicide, where self-defense is asserted, the defendant may introduce evidence of the turbulent or dangerous character of the decedent. Commonwealth v. Tiffany, 121 Pa. 165, 15 A. 462 (1888). This type of character evidence is admissible on either of two grounds: 1) to corroborate the defendant’s alleged knowledge of the victim’s violent character in an effort to show that the defendant reasonably believed that her life was in danger; and/or 2) to prove the allegedly violent propensities of the victim to show that the victim was in fact the aggressor. Commonwealth v. Clemmons, 505 Pa. 356, 479 A.2d 955 (1984); Commonwealth v. Amos, 445 Pa. 297, 284 A.2d 748 (1971). In the instant case, Weinert’s testimony is admissible on both of these grounds.
¶6Where this character evidence is proffered to corroborate the defendant’s state of mind, the defendant must demonstrate knowledge of the decedent’s character or reputation in order to establish a proper foundation for her claim that such knowledge put her in fear. Commonwealth v. Stewart, 483 Pa. 176, 180 n. 2, 394 A.2d 968, 970 n. 2 (1978); II Wigmore, Evidence § 246. As noted previously, appellant herein testified as to the numerous episodes of violence inflicted upon her by the decedent when he had *421been drinking. From this, it is obvious that appellant knew of the decedent’s character for violence when drinking.
¶7Having established her knowledge of the decedent’s violent character, appellant was entitled to buttress her claim with evidence of the decedent’s violent character. Appellant sought to introduce Weinert’s testimony to explain the decedent’s general character and reputation when drinking. At the very least, Weinert’s testimony would have shown that the decedent was “mean and vicious” when drunk. Since there was evidence to show that the decedent had been drinking prior to the stabbing,
¶8In addition, Weinert's testimony should have been admitted on the issue of who was the aggressor. This Court, as far back as 1884, has permitted the introduction of character evidence to prove the decedent’s violent propensities, where self-defense is asserted and where there is an issue as to who was the aggressor. Alexander v. Commonwealth, 105 Pa. 1, 9 (1884). “When the issue of self-defense is made in a trial for homicide, and thus a controversy arises whether the deceased was the aggressor, one’s persuasion will be more or less affected by the character of the deceased; it may throw much light on the probabilities of the deceased’s action.” I Wigmore, Evidence § 63 at 467.
¶9Weinert’s testimony was both relevant and competent evidence of the decedent’s character for violence when drinking and of his being the aggressor. The trial court erred in excluding such evidence.
¶10Accordingly, we reverse the order of the Superior Court and remand to the Court of Common Pleas for further proceedings consistent with this opinion.
¶11. Both the police officer at the scene and the appellant testified that the decedent appeared to have been drinking (T.T., 10/30/87, pp. 26-28 and 11/4/87 pp. 9, 35-36). The decedent’s son also testified that the decedent had been drinking earlier in the day (T.T., 10/30/87, p. 92).
¶12. The defendant’s knowledge of the decedent’s character is unnecessary if the character evidence is offered to prove that the decedent, with his violent propensities, was the aggressor. I Wigmore, Evidence § 63 at 470-471.
¶13. Incredibly, the trial court permitted the prosecution in rebuttal to present testimony that the decedent was normal and happy when drinking. This ruling is contradictory to the trial court’s prior ruling that the appellant could not present testimony as to the vicious nature of the decedent when he was drinking.