Thaddeus Curry appeals his convictions for murder and possession of a firearm during the commission of a violent crime in connection with the death of Heath Hamilton. On appeal, Curry argues (1) the trial court erred in limiting the scope of his cross-examination of two co-defendants on sentencing exposure they faced for murder and other charges related to Hamilton’s death, and (2) the trial court erred in charging the jury on “the hand of one is the hand of all” theory. We affirm.
FACTS
Shortly after midnight on March 18, 2003, Hamilton and Ronald Coursey drove to an apartment complex in Augusta, Georgia, to purchase marijuana. In the apartment complex’s parking lot, they encountered Anthony Savage and Curry and asked if they had any marijuana to sell. Curry and Savage said they had no marijuana, but agreed to procure some and sell a quarter pound’s worth to Hamilton and Coursey for $220.
Hamilton and Coursey drove to an ATM and withdrew money to pay for the drugs. Meanwhile, Curry, Savage, and Jeremy Simuel drove around Augusta looking for marijuana to sell to Hamilton and Coursey. They were unsuccessful. When they all returned to the apartment complex, Hamilton and Coursey followed Curry, Savage, and Simuel to Simuel’s apartment. Hamilton and Coursey waited outside the apartment while the others went inside and closed the door. They were soon informed the transaction would occur later.
Hamilton and Coursey left the apartment complex and went to Hamilton’s home in Beech Island in Aiken County, where they smoked marijuana and waited until Curry and Savage called. The parties spoke by phone and agreed to meet at a gas station in Beech Island. Although Curry, Savage, and Simuel failed to procure marijuana to sell Hamilton and Coursey, they apparently intended to meet under the guise of a drug sale in order to rob Hamilton and Coursey.
Hamilton and Coursey met Curry and Savage in a dark area behind the gas station. Curry and Savage exited their car, where Simuel remained seated. They approached the car in *678which Hamilton and Coursey waited. Savage told Hamilton they did not have any marijuana, but demanded to see the money. Within minutes, Hamilton was shot and killed while still seated in his vehicle with Coursey. Curry and Savage fled in the waiting car driven by Simuel.
Curry, Savage, and Simuel were charged in connection with the robbery and Hamilton’s murder. At Curry’s trial, Coursey, Savage, and Simuel implicated Curry in Hamilton’s murder. Coursey testified he had not met Curry, Savage, or Simuel before the night of the murder. He stated they first met around midnight in the dark parking lot of the apartment complex, a short time later at the apartment complex, and finally in the dark parking lot of the gas station where Hamilton was killed. He testified he called 911 after the shooting but was unable to provide many details about the perpetrators, telling the 911 dispatcher, “I don’t know, it’s dark[,] man, I just don’t know.” However, at trial Coursey testified Curry had the gun in his hand and that Savage never had possession of the gun. Moreover, he unequivocally identified Curry as the shooter.
Savage testified Curry carried a gun with him on the night of the murder and claimed he saw Curry fire the gun three or four times at the murder scene. Savage further testified that after the shooting, Curry and he fled in a car driven by Simuel. According to Savage, Curry exclaimed, “I think I dome capped him,” implying he shot Hamilton in the head. Savage testified Curry later told him he had disposed of the murder weapon. Simuel largely corroborated Savage’s testimony but did not provide an eyewitness account of Curry firing the gun.
Curry sought to question the motives and biases of Simuel and Savage by cross-examining them on the possible sentences they faced in connection with Hamilton’s murder. When Curry questioned Simuel about the possible sentences he faced, the trial court sustained the State’s objection and instructed the jury to disregard the testimony.
Prior to Savage’s testimony, Curry asked the trial court in limine to allow impeachment of Savage on bias and motive by questioning him about the possible sentences he faced for charges related to Hamilton’s death. The trial court denied *679his request. In reaching its decision, the trial court considered Curry’s request in light of State v. Mizzell, 349 S.C. 326, 563 S.E.2d 315 (2002), and stated:
Under [the circumstances in Mizzell], sir, part of the problem I think in that case was that, as I read it, the witness was given an offer to plead to one particular charge versus the potential sentence, the maximum sentence on the other charges that the defendant would have faced had she been convicted or tried on the original charges, and we don’t have that here. There’s no deal between the State at all.
Curry later sought clarification, asking, “So the Court is ruling that he says he has no deal, then I am prohibited from asking about these penalties that he’s facing, is that correct?” The trial court responded affirmatively. The trial court elaborated, “We’re not going to bring him out here to elicit whether or not he knows what his potential sentences are. As I understand it there’s no negotiations or deals between the State and this particular witness.”
The jury convicted Curry on both charges. He received concurrent prison sentences of five years for the firearms charge and life in prison for the murder charge. This appeal followed.
LAW/ANALYSIS
I. Scope of Cross-examination
Curry argues the trial court committed reversible error in denying his request to cross-examine Simuel and Savage concerning possible sentences he faced in connection with Hamilton’s death.1 We disagree.
*680To constitute error, a ruling to admit or exclude evidence must affect a substantial right. Rule 103(a), SCRE; State v. Johnson, 363 S.C. 53, 60, 609 S.E.2d 520, 524 (2005). However, error is harmless where it could not reasonably have affected the trial’s outcome. State v. Mitchell, 286 S.C. 572, 573, 336 S.E.2d 150, 151 (1985). In considering whether error is harmless, a case’s particular facts must be considered along with various factors including:
... the importance of the witness’ testimony in the prosecution’s case, whether the testimony was cumulative, the presence or absence of evidence corroborating or contradicting the testimony of the witness on material points, the extent of cross-examination otherwise permitted, and, of course, the overall strength of the prosecution’s case.
State v. Clark, 315 S.C. 478, 482, 445 S.E.2d 633, 635 (1994). Thus, an insubstantial error not affecting the result of the trial is harmless where “guilt has been conclusively proven by competent evidence such that no other rational conclusion can be reached.” State v. Bailey, 298 S.C. 1, 5, 377 S.E.2d 581, 584 (1989). A violation of a defendant’s Sixth Amendment right to confront a witness is not per se reversible error if the error is harmless beyond a reasonable doubt. State v. Graham, 314 S.C. 383, 385, 444 S.E.2d 525, 527 (1994).
In this case, Curry relied on State v. Mizzell, 349 S.C. 326, 563 S.E.2d 315 (2002), in support of his argument that he should be allowed to cross-examine his co-defendants as to any possible sentences they faced in connection with Hamilton’s death. In Mizzell, our Supreme Court found error in the trial court’s decision to exclude evidence of possible sentences faced by Mizzell’s co-defendant where the parties faced the same charges and the co-defendant had not yet pled guilty or reached a plea agreement with the State. The court found:
The fact the witness has yet to reach a plea bargain or been found guilty should not prevent the admission of such evidence. The lack of a negotiated plea, if anything, creates a situation where the witness is more likely to engage in biased testimony in order to obtain a future recommendation for leniency.
Id. at 333, 563 S.E.2d at 318.
Similar to the scenario in Mizzell, Curry’s co-defendants faced the same charges as Curry and had not pled guilty or *681reached a plea agreement. The trial court refused to allow Curry to cross-examine his co-defendants on the possible sentences they faced because Savage and Simuel had not pled guilty or reached a plea agreement with the State. We find this ruling contradicts the settled law established in Mizzell. Accordingly, we find the trial court erred in barring the cross-examination of Simuel and Savage on the possible sentences they faced.
However, the refusal to allow Curry to cross-examine his co-defendants on any possible sentences they faced in connection with Hamilton’s death was harmless. At trial, the testimony given by the co-defendants was not the only evidence of Curry’s involvement in the shooting of Hamilton. Ronald Coursey, the other victim of the robbery, unequivocally identified Curry as the shooter. He testified:
Coursey: And then the next I knew, he came up, Mr. Curry, over there had the gun.
Q: You saw Mr. Curry with the gun?
A: Yes, sir, he had the gun the whole time.
Q: What did he do with the gun?
A: ... he started shooting.
Q: Could you describe the gun?
A: ... it was either automatic or semi-automatic. It went off real fast.
Q: And how was [Curry] holding it?
A: In one hand.
Q: Okay. And so what did he say when he pulled the gun out?
A: I don’t think he said anything, it just happened too fast and he shot and hit [Hamilton] in the head.
Q: Did you see who pulled the trigger?
A: Yes, sir. It was Mr. Curry over there.
Moreover, in addition to Coursey, Javon Rushon provided the following testimony regarding a conversation he overheard between Curry and Savage regarding the murder weapon:
*682Q: What specifically did you hear Mr. Curry — what if anything, did you hear Mr. Curry mention about the gun?
A: “They would never find it.” “The hammer came off of it.” You know, “It was chopped up.”
On cross-examination, Rushon further clarified that it was in fact Curry who was talking about the gun, stating “Thaddeus Curry was talking to [Savage] about it.”
The testimony of the co-defendants, Simuel and Savage, was merely cumulative to that given by Coursey and Rushon. As a result, Curry’s guilt or innocence did not hinge solely on the testimony of his co-defendants; the testimony of Coursey and Rushon provided other competent evidence upon which a rational verdict of guilty could be based. Therefore, as the error on the part of the trial judge in limiting the scope of cross-examination could not have reasonably affected the outcome of the trial, it was harmless.
II. Jury Charge
Curry next argues the trial court erred in its charge on “the hand of one is the hand of all” theory. We disagree.
“A charge is sufficient if, when considered as a whole, it covers the law applicable to the case.” State v. Ezell, 321 S.C. 421, 425, 468 S.E.2d 679, 681 (Ct.App.1996). “The substance of the law is what must be charged to the jury, not any particular verbiage.” State v. Adkins, 353 S.C. 312, 318-19, 577 S.E.2d 460, 464 (Ct.App.2003). “Jury instructions must be considered as a whole and, if as a whole, they are free from error, any isolated portions which might be misleading do not constitute reversible error.” State v. Jackson, 297 S.C. 523, 526, 377 S.E.2d 570, 572 (1989).
At trial, Curry argued the court’s proposed charge on “the hand of one is the hand of all” theory lacked “sufficient emphasis on the issue of probable or natural consequence .... ” Based on language drawn from State v. Dickman, 341 S.C. 293, 534 S.E.2d 268 (2000), Curry suggested the following charge:
[I]f two or more combine together to commit an unlawful act and a crime is committed by one of the actors as a probable and natural consequence of the acts done in pursuance of *683the common design, all present and participating in the unlawful undertaking are as guilty as the one who committed the act.
(emphasis added).
The trial judge rejected Curry’s proposed charge. He subsequently charged the jury twice on “the hand of one is the hand of all” theory. The first charge, which he gave along with the other charges prior to jury deliberations, stated:
It is my duty to charge you now that if a crime is committed by two or more people who are acting together in committing a crime, the act of one is the act of all. If a person joins with another to accomplish an illegal purpose, he is criminally responsible for everything done by the other person which occurs as a natural consequence of the acts done in carrying out the common plan and purpose.
After the jury left to deliberate, Curry renewed his objection to the charge on the basis that “the instruction as given did not convey to the jury that the act in this case, a homicide, must be a natural or probable consequence of the preexisting plan in order ... for the theory of the hand of one, hand of all to apply----” (emphasis added). The trial judge noted Curry’s exception.
During its deliberation, the jury asked the court to recharge “the hand of one is the hand of all.” The court brought the jury out and charged accomplice liability as follows, in pertinent part:
[I]f a crime is committed by two or more people who are acting together in committing a crime, the act of one is the act of all. I tell you further that a person who joins with another to accomplish an illegal purpose is criminally responsible for everything done by the other person which occurs as a natural consequence of the acts done in carrying out the common plan or purpose. When two or more people are acting together ... assisting each other in committing the offense the act of one is the act of all, or as is sometimes said, the hand of one is the hand of all.
(emphasis added).
South Carolina courts frequently approve accomplice liability charges that lack language stating an accomplice’s criminal act must be “a probable and natural consequence” of the *684accomplice’s common plan. For instance, in State v. Langley, 334 S.C. 643, 515 S.E.2d 98 (1999), our supreme court stated that under “the hand of one is the hand of all” theory, “one who joins with another to accomplish an illegal purpose is liable criminally for everything done by his confederate incidental to the execution of the common design and purpose.” In State v. Kelsey, 331 S.C. 50, 76-77, 502 S.E.2d 63, 76 (1998), the supreme court approved a broader accomplice liability charge that stated, “... if a crime is committed by two or more persons who are acting together in the commission of a crime, then the act of one is the act of both.” Moreover, in State v. Crowe our Supreme Court approved the following charge for accomplice liability:
[T]wo or more combine together to commit an unlawful act, such as robbery, and, in the execution of that criminal act, a homicide is committed by one of the actors, as a probable or natural consequence of the acts done in pursuance of the common design, all present participating in the unlawful undertaking are as guilty as the one who committed the fatal act. This principle was stated in State v. Cannon, 49 S.C. 550, 27 S.E. 526: “The common purpose may not have been to kill and murder, but if it was unlawful, as, for instance, to break in and steal, and in the execution of this common purpose a homicide is committed by one, as a probable or natural consequence of the acts done in pursuance of the common design, then all present participating in the unlawful common design are as guilty as the slayer.”
258 S.C. 258, 265, 188 S.E.2d 379, 382 (1972) (emphases added). Therefore, the approval of this charge demonstrates that the “natural and probable consequence” language need not be included in the charge, as requested by Curry, if the charge as a whole adequately conveys the law. Additionally, with the approval of the disjunctive “or” in the “probable or natural consequence” language of State v. Crowe, the trial court’s charge arguably benefited Curry as it only included the “natural consequences” rather than the “natural or probable” language.
Therefore, when viewing the challenged portion of the jury charge as a whole with the rest of the trial court’s instruction, *685we find the trial court adequately charged the law regarding “hand of one hand of all.”
CONCLUSION
For the forgoing reasons, Curry’s conviction is hereby
AFFIRMED.
GOOLSBY, J. concurs. ANDERSON, J. dissents in a separate opinion.. Curry also argues the trial court erred in refusing to allow him to cross-examine Savage about pending criminal charges unrelated to Hamilton's murder. Curry never proffered the evidence or even attempted to proffer it. The evidence is not part of the record. Thus, the issue is not preserved. See State v. Hawkins, 310 S.C. 50, 54, 425 S.E.2d 50, 57 (Ct.App.1992) (declining to rule on alleged error in exclusion of evidence, where no proffer was made and excluded evidence was not part of record). Lastly, Curry argues the trial court erred in admitting evidence that he was incarcerated. This issue is not preserved for appellate review. See State v. Dunbar, 356 S.C. 138, 142, 587 S.E.2d 691, 694 (2003) ("A party may not argue one ground at trial and an alternate ground on appeal.”).