OPINION
LANE, Judge:This felony-murder case arises out of an arson fire which destroyed the home of Mary Castillo, and killed two of her five children in Frederick, Oklahoma, on June 6, 1987. Appellant, Gilberto Hernandez Martinez, was convicted of two counts of Murder in the First Degree in Tillman County District Court, Case No. CRF-87-48. The jury recommended a sentence of death on each count which the trial court imposed. Two errors require reversal of judgment and sentence and remand to the district court for retrial.
The defendant’s Sixth Amendment right to confront eye-witness David Castillo was violated when the trial court granted the State’s motion in limine which barred cross-examination regarding bias; and the jury was not instructed on the available sentencing option of life without the possibility of parole. We address only those issues requiring reversal.
While Mary Castillo was out with friends and her children were home alone, someone set fire to her house. Her three boys, David, Louis and Angel, escaped. Her daughters, Margaret and Reynalda, died from carbon monoxide poisoning. The only contested issue at trial was who set the fire. Uncontro-verted evidence established gasoline was poured along the baseboards of the living room, in two of the three bedrooms used by the children, and on the front door jamb. The two younger boys, Louis and Angel, shared a room, as did the two girls. Gasoline was poured in a pool in the middle of the boys’ room, and around Reynalda’s mattress. David had a room of his own and no gasoline was used there.
Gilberto Hernando Martinez is Mary Castillo’s boyfriend, and Margaret’s father. The State believed Martinez set the fire in revenge for Ms. Castillo dancing with another man at the Paso Del Norte bar earlier that evening. Martinez started a scuffle with her at the bar and knocked off her cowboy hat. As he left, he said in Spanish, “tu .vas a pager”, which was translated in the record as, “you are going to pay”. No witness knew to whom this statement was directed.
Two teenagers saw the appellant in the vicinity of the Castillo home around 1:00 and 1:30 a.m. One saw him carrying something under his arm. The house was engulfed by flame at 4:00 a.m. when a neighbor called the fire department.
*140Eleven year old David Castillo, the only eye-witness,1 testified he was awakened by smoke, got up, and went into the kitchen. He was fully dressed. While hiding in the kitchen he saw the appellant pour gasoline out of a yellow container onto existing flames in the living room, and then go into the girls’ room. David testified that as Martinez left the house he poured gasoline at the front door and set the gas on fire. David was able to wake up his brothers and save them, but by the time he got to his sisters’ room, the intensity of the fire forced him back. He testified that when he got out of the house he saw the appellant running away.
David Castillo had a history of setting fires when his mother left him alone in charge of his younger brothers and sisters. He had set three fires in homes the family had rented. Two of these resulted in evictions of the family. He had also set fire to a garage and a car. The State filed a motion in limine to keep this evidence from the jury. The trial court sustained the State’s motion.
I. ISSUES RELATING TO GUILT AND INNOCENCE
A. SUFFICIENCY OF THE EVIDENCE
In his first proposition of error the Appellant argues the State presented insufficient evidence to prove he set the arson fire. He correctly cites the standard of review when both direct and circumstantial evidence are presented: viewing the evidence in the light most favorable to the prosecution, could any rational trier of fact have found each element of the crime beyond a reasonable doubt. See Riley v. State, 760 P.2d 198, 199-200 (Okl.Cr.1988); Drew v. State, 771 P.2d 224, 227 (Okl.Cr.1989). Appellant then misapplies the standard.
David Castillo’s testimony was corroborated by the State’s arson inspector. The char patterns left by the accelerant are consistent with the places David testified he saw the appellant pour gasoline. This evidence, if believed, when viewed in the light most favorable to the prosecution, is sufficient to allow any rational trier of fact to find Martinez set the fire which killed the Castillo girls.
B. DENIAL OF CONFRONTATION: CROSS-EXAMINATION OF DAVID CASTILLO
The sufficiency of the evidence, however, depends on the credibility of David Castillo. Unknown to the jury, this witness’ credibility could have been severely impeached by the fact he set fires when his mother was out, and could have a reason to avoid blame for this one. This information was excluded from trial when the trial court granted the State’s motion in limine which provided:
Comes now the State of Oklahoma and moves this Court for an order in limine to limit the defense herein. It has come to the attention of the State that the defense herein intends to discredit the witness David Castillo by trying to show prior bad acts involving the setting of fires. That State moves for an order in limine directing that any such demonstration of prior bad acts by the witness be limited to actual convictions of a crime or juvenile ajudica-tions (sic) if any, of the witness David Castillo.
The State successfully defended its motion twice: prior to the defense cross-examination of David Castillo, and prior to the defense calling David Castillo as its own witness. On each occasion defense counsel argued he wanted to show David set the fires. This argument was successfully defeated by the prosecutors.
The State skillfully used sections of the Evidence Code to bar admission of this evidence. The prosecutor argued Section 2404(B) prohibits the introduction of prior bad acts to show a person acted in conformity therewith. This is correct. See 12 O.S. 1981, § 2404(B). The State also argued setting fires is not an act probative of untruthfulness and thus the evidence was also barred under Section 2608(B). Again, this is correct. See 12 O.S.1981, § 2608(B). De*141fense counsel then argued the prior fires were admissible under Section 2405 to show habit or practice and the witness’ conformity to his habit. The trial court correctly found counsel’s argument unpersuasive. See 12 O.S.1981, §§ 2405 and 2406.
While the trial court properly ruled on the argument as presented, we do not end our review here. It is plain the defendant was denied his constitutional right under the Confrontation Clause of the Sixth Amendment to cross-examine David Castillo regarding his bias and motive to lie. See Beck v. State, 824 P.2d 385 (Okl.Cr.1991); Delaware v. Van Arsdall, 475 U.S. 673, 106 S.Ct. 1431, 89 L.Ed.2d 674 (1986); Davis v. Alaska, 415 U.S. 308, 94 S.Ct. 1105, 39 L.Ed.2d 347 (1974). The State concedes this point in its brief by arguing:
Defense counsel can ask David if he set the fires.(sic) If he says no, defense counsel under Davis, 415 U.S. at 316, [94 S.Ct. at 1110], was certainly entitled to ask David about the other fires to show bias.
The State concludes by arguing, without citation, that the defense waived any error because counsel did not ask David if he set the fire. It is this very argument which points up the confrontation violation in this ease. Defense counsel could not ask David whether he set the fire, for under the trial court’s ruling, he was prohibited from confronting David with the other fires and challenging David’s response. Under these circumstances we find plain error which was not waived.
Had the trial judge and counsel had the benefit of our decision in Beck, this error may have been avoided. In Beck this Court reemphasized the fundamental principle that bias evidence is never collateral and a witness may be cross-examined about any matter tending to show his bias or prejudice. 824 P.2d at 388.
Three factors govern admissibility of this evidence: it must be (1) relevant, (2) otherwise admissible under constitutional and statutory authority, and (3) its probative value must not be substantially outweighed by the danger of unfair prejudice. Id. at 389 (citing 12 O.S.1981, §§ 2401, 2402 and 2403). The evidence of David’s history of setting fires, and his possible motive to avoid blame for this one, satisfies each of these conditions. First, the evidence is relevant of possible motive to lie. It is also otherwise admissible, for extrinsic evidence on the issue of bias may be admitted. See Id. Finally, the evidence carries with it little if any danger of unfair prejudice, and it is extremely probative of motive to lie. Upon the final weighing for admission, the probative value of this evidence is not substantially outweighed by the danger of unfair prejudice.
Having found the defendant was denied his right to confront David Castillo, we must determine whether this error is harmless. The two-step analysis for determining whether constitutional error may be found harmless was set forth in Bartell v. State, 881 P.2d 92 (Okl.Cr.1994). We first examine the error itself and determine whether it is subject to harmless error review at all; and if it is, we then determine whether the error was indeed harmless beyond a reasonable doubt. Id. at 97. Constitutional error which pervades the entire trial is not subject to harmless error analysis; constitutional error which occurs during the presentation of the ease is. Id. at 98.
The denial of cross-examination of one witness is a discrete act which occurred during the presentation of the case and thus may be found harmless. The error may be declared harmless only if this Court finds beyond a reasonable doubt that it did not affect the outcome of the ease. Id. at 97 (citing Chapman v. California, 386 U.S. 18, 23-24, 87 S.Ct. 824, 827-28, 17 L.Ed.2d 705 (1967)).
Evidence identifying the appellant as the one who set the fire consisted of testimony by neighbors who saw him in the vicinity of the home and by David Castillo who testified he saw the appellant pour gasoline in the home and light the matches setting it ablaze. If the jury doubted David Castillo’s credibility, the neighbors’ testimony is insufficient to convict. In trial context, it was the credibility of David Castillo which determined whether the defendant would be convicted or acquitted. Given the pivotal importance of this *142testimony, we do not find that denying the defendant his right to expose the possible bias of this witness was harmless beyond a reasonable doubt. This error requires reversal of judgment and remand for new trial.
II. SENTENCING STAGE: FAILURE TO INSTRUCT ON LIFE WITHOUT PAROLE
The appellant was tried four months after the effective date of the legislative amendment to Title 21 O.S.Supp.1987, § 701.10 which granted the sentencing option of life without parole in cases of first degree murder. Unfortunately the jury was not instructed on this sentencing option. Had this error occurred alone it would have required vacation of sentence and remand for resentencing. See Fontenot v. State, 881 P.2d 69 (Okl.Cr.1994); Salazar v. State, 852 P.2d 729 (Okl.Cr.1993); Humphrey v. State, 864 P.2d 343 (Okl.Cr.1993), cert. denied, — U.S. -, 114 S.Ct. 1663, 128 L.Ed.2d 379 (1993); Hain v. State, 852 P.2d 744 (Okl.Cr.1993), cert. denied, — U.S. -, 114 S.Ct. 1402, 128 L.Ed.2d 75 (1994); Wade v. State, 825 P.2d 1357 (Okl.Cr.1992); Allen v. State, 821 P.2d 371 (Okl.Cr.1991).
JOHNSON, P.J., and CHAPEL, V.P.J., and STRUBHAR, J., concur. LUMPKIN, J., concurs in result.. His six year old brother, Angel, also testified as an eyewitness. On direct he testified he saw Martinez in his room the night of the fire; on cross he testified he did not see Martinez in his room the night of the fire, but saw him earlier in the day. The testimony thus can be given no weight.