OPINION ON APPELLANT’S PETITION FOR DISCRETIONARY REVIEW
CAMPBELL, Judge.Appellant was convicted, after a jury trial, of unauthorized use of a motor vehicle. V.T.C.A., Penal Code § 31.07. The jury assessed a punishment of imprisonment for 20 years, enhanced under V.T.C.A., Penal Code § 12.42(a). The Fourteenth Court of Appeals affirmed in an unpublished opinion, Woodfox v. State, No. B14-85-155-CR (Tex.App. — Houston [14th] April 17, 1986). We granted the appellant’s petition for discretionary review to determine whether a non-testifying defendant can raise the defense of mistake of fact through a second party such as to receive an instruction by the trial court.1 We hold that he may and we will remand to the Court of Appeals.
On June 4, 1984, complainant, Sherry Ferrel stopped her car at a service station. Leaving the car running, she placed a call at a pay phone. Two men jumped into her car and drove it away. Ms. Ferrel told her friend on the phone what had happened, and he called the police. The next day, Houston police officers Crosby and McCor-vey saw appellant driving complainant’s car at a high rate of speed. The officers ran a check on the license plate and learned that the car had been stolen. They called for assistance and when two additional police cars responded to their call, they stopped appellant, who was the only occupant of Ms. Ferrel’s car. The officers arrested appellant for auto theft. Appellant was read his rights, and he told the police that he had borrowed the car from William Davis. He was then taken to the police department’s auto theft division.
At trial, the State called Ms. Ferrel and both arresting officers as witnesses. Both of the officers testified that the appellant *409told them that he had gotten the car from William Davis an hour before appellant’s arrest. Appellant did not take the stand or introduce any evidence. Before the charge was read to the jury, appellant’s attorney asked for an instruction on mistake of fact, pursuant to V.T.C.A., Penal Code § 8.02. The judge refused this request.
Citing Williams v. State, 605 S.W.2d 596 (Tex.Cr.App.1980), and Harper v. State, 533 S.W.2d 776 (Tex.Cr.App.1976), the Court of Appeals held that the arresting officers’ testimony “alone is insufficient to support the submission of the [mistake of fact] instruction.” Woodfox v. State, supra at 2.
Appellant argues that Williams, supra, and Harper, supra, should be distinguished from the instant case because in neither Williams nor Harper did counsel request an instruction on the affirmative defense of mistake of fact. Instead, the requested instructions concerned definitions of “consent” and “ownership”.
Appellant, additionally, contends that the Court of Appeals opinion is inconsistent with our decision in Lynck v. State, 643 S.W.2d 737 (Tex.Cr.App.1983). Lynch, supra, held that a defendant who testified that he borrowed the stolen car from a person who he believed was its rightful owner was entitled to an instruction on mistake of fact.
In its brief, the State argues that the evidence raised no issue of mistake of fact and that there was no evidence that appellant believed that William Davis was the owner of the car. The State seeks to distinguish Lynch, supra, on the ground that the defendant in Lynch testified, whereas the appellant in the instant case did not.
“In determining whether any defensive charge should be given, the credibility of evidence or whether it is controverted or conflicts with other evidence in the case may not be considered. When a defensive theory is raised by evidence from any source and a charge is properly requested, it must be submitted to the jury.” Gavia v. State, 488 S.W.2d 420, 421 (Tex.Cr.App.1972). See also, e.g., Sanders v. State, 707 S.W.2d 78, 80 (Tex.Cr.App.1986)2; Booth v. State, 679 S.W.2d 498, 501 (Tex.Cr.App.1984); Moon v. State, 607 S.W.2d 569, 570 (Tex.Cr.App.1980); Green v. State, 566 S.W.2d 578, 584 (Tex.Cr.App.1978); Cain v. State, 549 S.W.2d 707, 713, cert. denied 434 U.S. 845, 98 S.Ct. 149, 54 L.Ed.2d 111 (Tex.Cr.App.1977); McKenzie v. State, 521 S.W.2d 637, 639 (Tex.Cr.App.1975); Thompson v. State, 521 S.W.2d 621, 625 (Tex.Cr.App.1974); Hubbard v. State, 153 Tex.Cr.R. 143, 217 S.W.2d 1019, 1020 (1949). This well-established principle has been applied specifically to a defendant charged with unauthorized use of a motor vehicle who requested a jury instruction concerning his mistaken belief that he was borrowing the stolen car from its rightful owner. Lynch v. State, supra. This rule is designed to insure that the jury, not the *410judge, will decide the relative credibility of the evidence. Gauthier v. State, 496 S.W.2d 584, 585 (Tex.Cr.App.1973). When a judge refuses to give an instruction on a defensive issue because the evidence supporting it is weak or unbelievable, he effectively substitutes his judgment on the weight of the evidence for that of the jury. Id. The the weight of evidence in support of an instruction is immaterial. E.g., Booth v. State, supra.
Both Williams and Harper have facts which are essentially identical to the facts in the instant case. In Williams and Harper, defendants were driving a stolen car when they was stopped by the police. The defendants told the arresting officers ’that the cars were obtained from some specified person. At both trials, the arresting officers testified to defendants’ out of court statements while the defendants themselves chose not to testify.
The relevant language in Williams states:
It has long been the rule in this State that in felony cases it is necessary to give instructions which are applicable to every legitimate deduction form the facts. Literally dozens of cases are cited in 12A Tex.Digest, Criminal Law, Key No. 770(2) (1961). The rule and supporting authorities were set out in detail in Gauthier v. State.
But the rule is not applicable here. In Bonner v. State, this Court reversed a conviction upon similar facts; but the distinction there is that the defendant testified that he did not know the car was stolen and that he had been given the car to use by his friend James. This Court held that this was sufficient to raise the defensive issue and to require the court to charge the jury thereon. In our case, the appellant did not testify, the only evidence being the officer’s testimony as to appellant’s exculpatory statement. In this respect, the decision in Harper v. State is dispositive.
605 S.W.2d at 599 (citations omitted).
Appellant suggests that we avoid the holdings in Harper and Williams by distinguishing them from the facts in the instant case. We recognize appellant is correct when he points out that in neither of those cases was there a request for an instruction on mistake of fact. We do not find this distinction to be meaniningful. Within the context of Harper and Williams, the requested instructions on “ownership” and “consent” were tantamount to and had the same effect as a mistake of fact instruction. We therefore find appellant has advanced a distinction without a difference.
We now find it necessary to confront the holding in Williams and Harper. This Court effectively departed from the general rule “that entitles a defendant to an affirmative submission of defenses raised by the evidence.” Lynch, supra at 738. We think such a departure violates the general rule, which requires the jury to be the ultimate arbiter of facts. This departure further implicates an accused’s right not to testify, pursuant to Article I, sec. 10 of the Texas Constitution and the Fifth Amendment to the United States Constitution. Predicating a defendant’s right to a jury instruction upon his taking the stand suggests, at the very least, a mild form of compulsion to testify. As this court has stated:
The right of an accused party to be free from the fear of compelled self-incrimination and to remain silent is a vital protection which our society provides a citizen accused of a criminal offense. This personal right cannot in any way be abridged....
Jones v. State, 693 S.W.2d 406, 407 (Tex.Cr.App.1985). Given the importance of the rights protected by the Fifth Amendment and Article I, section 10 and the lack of any compelling reason for the continued vitality of the Williams and Harper exception, we find it preferable to overrule them in so far as they conflict with today’s holding.
Appellant’s petition was granted so that this Court could answer the limited question of whether a defendant must always offer evidence in order to be entitled to an instruction on mistake of fact. Having answered that question in the negative, we express no opinion as to the ultimate outcome of this ease.
*411This case is remanded to the Court of Appeals for action not inconsistent with this opinion.
. What we have stated in the body of the opinion is appellant’s ground for review. The reason for entertaining review is that the Court of Appeals decision is in conflict with decisions from this Court. Lynch v. State, 643 S.W.2d 737 (Tex.Cr.App.1983); Gavia .v. State, 488 S.W.2d 420 (Tex.Cr.App.1973). See Tex.R.App.Pro. 200 (c)(3).
. In Sanders, defendant was charged with burglarizing a pawn shop and removing a guitar. Defendant claimed that he had bought the guitar from an unidentified man, about 5 minutes before the police arrived. In order to be convicted for burglary, a jury must find that the defendant (1) entered a building, (2) without the effective consent of the owner, (3) with the intent to commit a felony or a theft. V.T.C.A., Penal Code § 30.02(a)(1). Had the jury believed defendant’s story, they would have necessarily believed that he neither entered the store nor took the guitar. Because the defense theory merely negated an element of the offense, no instruction was needed. Sanders, supra at 81.
The offense of unauthorized use of a motor vehicle requires that the defendant (1) intentionally operates a motor-powered vehicle, (2) without the effective consent of the owner. V.T. C.A., Penal Code § 31.07(a). If a jury were to believe the defense theory in the instant case, they could still find intentional operation of a motor vehicle and lack of effective consent. The testimony^ established both of these elements, and the alleged mistake of fact is not inconsistent with either element. The notion that appellant’s mistaken belief is a defense to the offense alleged can not be found in the statute, itself. Section 8.02 of the Penal Code is the only statutory source which makes a mistake of fact a defense to section 31.07.
A failure to instruct on good faith purchase in Sanders did not deprive the jury of any essential statutory information. The charge on the elements of the offense was adequate. In the instant case, mistake of fact is a defense only by virtue of a separate section of the code. The charge, as delivered to the jury, failed to provide them with information which was necessary to place all evidence in its proper legal context.