¶1 We are asked to determine whether plaintiffs in a malpractice action against their former criminal defense attorneys were properly required to prove by a preponderance of the evidence that they were actually innocent of the underlying criminal charges. The Court of Appeals concluded that, as an element of their negligence claim, plaintiffs were required “to prove innocence in fact and not merely to present evidence of the government’s inability to prove guilt.” Ang v. Martin, 118 Wn. App. 553, 558, 76 P.3d 787 (2003). We affirm the Court of Appeals.
Owens, J.FACTS
¶2 Psychiatrist Jessy Ang and his wife Editha jointly owned Evergreen Medical Panel, Inc., a company that provided the Washington State Department of Labor and Industries with independent medical examinations of injured workers. As a result of Dr. Aug’s contact with a target of a governmental task force investigating social security fraud, Dr. Ang himself became a person of interest. In February 1994, the task force executed a search warrant on Dr. Aug’s office and seized copies of two sets of signed tax returns that reported conflicting amounts of income. The Angs were arrested in April 1996, following the execution of a search warrant at their residence. A year later, the Angs were indicted on 18 criminal counts, including conspiracy to defraud the United States, bank and tax fraud, and filing false statements.
¶3 The Angs retained defendants Richard Hansen and Michael G. Martin for flat fees of $225,000 and $100,000, respectively. Attorneys Hansen and Martin engaged in a *480round of plea negotiations prior to trial, but the Angs rejected the plea bargain. The case proceeded to a jury trial before Judge Tanner in federal district court in December 1997. On the fifth day of trial, just prior to the conclusion of the government’s case, Hansen and Martin recommended that the Angs accept another proffered plea, one that the Angs viewed as the least attractive of any agreement previously presented. After Dr. Ang was allegedly told that Mrs. Ang could face sexual assault in prison, the Angs agreed to plead guilty to 2 of the 18 counts.
¶4 The Angs then engaged attorney Monte Hester to review the plea discussions and provide a second opinion. Hester concluded that the government had not met its burden of proof and that the plea agreement provided the Angs with no material benefit. Retaining Hester and Keith A. MacFie to represent them, the Angs successfully moved to withdraw the pleas, which Judge Tanner had never formally accepted. In September 1999, the matter again proceeded to trial before Judge Tanner, with the Angs waiving their right to a jury. Although the government offered another plea bargain prior to trial, one requiring no plea on Dr. Ang’s part, a misdemeanor or felony for Mrs. Ang, and a $500,000 fine, the Angs rejected the plea and were acquitted on all 18 counts.
¶5 The Angs, along with Evergreen Medical, filed the present legal malpractice action against Hansen and Martin in May 2000 in Pierce County Superior Court. The complaint stated claims for legal malpractice and for violations of the Washington Consumer Protection Act, chapter 19.86 RCW. The trial court denied the defendants’ motion for summary judgment, and a jury trial began in November 2001. The trial court instructed the jury that the Angs had to prove by a preponderance of the evidence that they were innocent of the underlying criminal charges. On January 11,2002, responding to the initial two questions on a special verdict form, the jury found that the Angs had not “proven by a preponderance of the evidence [they were] innocent of all the criminal charges against [them].” Clerk’s Papers at *4811663-64. As to the verdict form’s third question, asking whether “any of the defendants [had been] negligent,” the jury made a finding of negligence against Martin only. Id. at 1664.
|6 The plaintiffs appealed, but the Court of Appeals affirmed. This court granted the plaintiffs’ petition for review.
ISSUES
¶7 (1) Where a legal malpractice suit stems from the representation of clients in a criminal prosecution, must plaintiffs who were acquitted of the criminal charges prove their actual innocence of the crimes, or does their acquittal satisfy the innocence element of their malpractice action?
18 (2) Did the Angs properly request review of jury instruction 13, which directed the jury to determine the Angs’ innocence of the criminal charges but provided no legal definitions of the named crimes, relying instead on the jury’s access to the proposed instructions from the criminal trial?
ANALYSIS
¶9 Standard of Review. The Angs contend that the trial court erred in requiring them to prove, in their malpractice suit against former defense counsel, their actual innocence of the underlying criminal charges. They also assert that the court inadequately instructed the jury on the definitions of those charges. As with all questions of law, the issues presented here are reviewed de novo. Kommavongsa v. Haskell, 149 Wn.2d 288, 295, 67 P.3d 1068 (2003).
¶10 Essential Elements of Legal Malpractice Claims against Criminal Defense Counsel. A plaintiff claiming negligent representation by an attorney in a civil matter bears the burden of proving four elements by a preponderance of the evidence:
*482(1) The existence of an attorney-client relationship which gives rise to a duty of care on the part of the attorney to the client; (2) an act or omission by the attorney in breach of the duty of care; (3) damage to the client; and (4) proximate causation between the attorney’s breach of the duty and the damage incurred.
Hizey v. Carpenter, 119 Wn.2d 251, 260-61, 830 P.2d 646 (1992); Bowman v. John Doe Two, 104 Wn.2d 181, 185, 704 P.2d 140 (1985) (noting that, in legal malpractice suits, proof of attorney-client relationship is grafted onto customary elements of negligence claim). The fourth element, proximate causation, includes “[clause in fact and legal causation.” Hartley v. State, 103 Wn.2d 768, 777, 698 P.2d 77 (1985). Cause in fact, or “but for” causation, refers to “the physical connection between an act and an injury.” Id. at 778. In a legal malpractice trial, the “trier of fact will be asked to decide what a reasonable jury or fact finder [in the underlying trial or ‘trial within the trial’] would have done but for the attorney’s negligence.” Daugert v. Pappas, 104 Wn.2d 254, 258, 704 P.2d 600 (1985) (emphasis added). Legal causation, however, presents a question of law: “It involves a determination of whether liability should attach as a matter of law given the existence of cause in fact.” Hartley, 103 Wn.2d at 779. To determine whether the cause in fact of a plaintiff’s harm should also be deemed the legal cause of that harm, a court may consider, among other things, the public policy implications of holding the defendant liable. Id. In “criminal malpractice” suits,1 two elements related to proximate causation have been added. In Falkner v. Foshaug, 108 Wn. App. 113, 29 P.3d 771 (2001), the Court of Appeals “conclude [d] that postconviction relief is a prerequisite to maintaining [a criminal malpractice] suit and proof of innocence is an additional element a criminal defendant/malpractice plaintiff must prove to prevail at trial in his legal malpractice action.” Id. at 124 *483(emphasis added); see also id. at 123 (referring to "an actual innocence requirement”).
¶11 The trial court in the present case thus instructed the jury as follows on the elements of the Angs’ criminal malpractice claims:
To prove their legal malpractice claims, the plaintiffs bear the burden of proving by a preponderance of the evidence each of the following:
First, that there is an attorney-client relationship giving rise to a duty owed by a defendant to a plaintiff;
Second, that plaintiffs have obtained a successful challenge to their convictions based on their attorney’s failure to adequately defend them;
Third, that plaintiff was innocent of the crimes charged; Fourth, that there is an act of omission by a defendant that breached the duty of care of an attorney;
Fifth, that a plaintiff was damaged; and
Sixth, that a breach of duty by a defendant is a proximate cause of a plaintiff’s damages . . . .[2]
The Angs assigned error to this instruction, contending that their undisputed acquittal of the criminal charges met not only the additional element of postconviction relief but also the innocence requirement.
¶12 By successfully withdrawing their guilty pleas and receiving an acquittal on all charges, the Angs unquestionably received the equivalent of postconviction relief,3 * but *484contrary to their contention, they did not thereby satisfy the Falkner court’s innocence requirement. The Angs mistakenly claim that, under Falkner, they were simply required to prove legal innocence, not actual innocence. See Shaw v. Dep’t of Admin., 861 P.2d 566, 570 n.3 (Alaska 1993) (Shaw II) (noting that “ ‘[Ilegal’ guilt or innocence is that determination made by the trier of fact in a criminal trial,” whereas “ ‘[a]ctual’ guilt is intended to refer to a determination in a civil trial, by a preponderance of the evidence, that the defendant engaged in the conduct he was accused of in the prior criminal proceeding”). But the Falkner court referred explicitly to the “actual innocence requirement” and at no point equated the innocence requirement with legal innocence.4 Plainly, a requirement of legal innocence would have been redundant alongside the additional, unchallenged requirement of postconviction relief and would have necessitated a confusing overlay of standards of proof, requiring the malpractice jury to consider whether the Angs had proved by a preponderance of the evidence that they would not have been found guilty beyond a reasonable doubt in the underlying criminal trial. See Wiley v. County of San Diego, 19 Cal. 4th 532, 966 P.2d 983, 990, 79 Cal. Rptr. 2d 672 (1998) (observing that, as to dual standards of proof, “mental gymnastics required to reach an intelligent verdict would be difficult to comprehend much less execute”).
¶13 Moreover, proving actual innocence, not simply legal innocence, is essential to proving proximate causation, both cause in fact and legal causation. Falkner, 108 Wn. App. at 115 (noting that criminal malpractice plaintiff must prove *485that “deficient representation, not his illegal acts, . . . [was] the proximate cause” of harm). Unless criminal malpractice plaintiffs can prove by a preponderance of the evidence their actual innocence of the charges, their own bad acts, not the alleged negligence of defense counsel, should be regarded as the cause in fact of their harm. Likewise, if criminal malpractice plaintiffs cannot prove their actual innocence under the civil standard, they will be unable to establish, in light of significant public policy considerations, that the alleged negligence of their defense counsel was the legal cause of their harm. Summarizing the policy concerns, the Falkner court observed that, “[requiring a defendant to prove by a preponderance of the evidence that he is innocent of the charges against him will prohibit criminals from benefiting from their own bad acts, maintain respect for our criminal justice system’s procedural protections, remove the harmful chilling effect on the defense bar, prevent suits from criminals who ‘may be guilty, [but] could have gotten a better deal,’ and prevent a flood of nuisance litigation.” 108 Wn. App. at 123-24 (footnotes omitted) (quoting Stevens v. Bispham, 316 Or. 221, 851 P.2d 556, 565 (1993)).
¶14 In the alternative, the Angs argue that, if a plaintiff’s actual guilt or innocence has any place in a criminal malpractice suit, the issue should be raised as an affirmative defense, not as an element of the plaintiff’s cause of action. The Angs find support in Shaw II, the only decision adopting the actual innocence requirement and shifting to the criminal malpractice defendant “the burden of proof by a preponderance of the evidence as to the actual guilt of the plaintiff.” 861 P.2d at 572. As respondent Martin explained, however, “[t]he criminal defendant/malpractice plaintiff is in a far better position to bear the burden of establishing innocence,” since, unlike his defense attorney, he “knows if he is actually innocent,” “was, presumably, present or involved in the underlying events which led to the criminal charges,” “has unlimited access to the information about his own acts necessary to prove innocence,” “would know what, if any, inculpatory facts he withheld from his lawyer,” and *486would have the “opportunity to accept a plea, potentially an Alford plea [North Carolina v. Alford, 400 U.S. 25, 91 S. Ct. 160, 27 L. Ed. 2d 162 (1970)] which could preserve his malpractice claim, before all facts and witness testimony have been developed or are known to his or her attorney.” Suppl. Br. of Resp’t Martin at 13. We find this practical analysis persuasive and thus decline to adopt the minority position of Shaw II.
¶15 In sum, we conclude that the Angs were properly required to prove by a preponderance of the evidence that they were actually innocent of the underlying criminal charges. We therefore affirm the Court of Appeals.
¶16 Plaintiffs’ Challenge to Adequacy of Jury Instructions on Underlying Criminal Charges. Instructing the jury that the Angs were required to prove their innocence of the criminal charges, the court identified those charges as “Tax Fraud, Bank Fraud, False Statement, and Conspiracy.” Jury Instruction 13, Br. of Appellants, App. 3. When the jury interrupted its deliberations to ask the court for the legal definitions of the charges, the court, in concert with counsel, advised the jury to “review carefully this Court’s instructions and the evidence (testimony and exhibits) admitted into evidence.” 27 Verbatim Report of Proceedings at 3822-30. (Among the exhibits admitted into evidence were the government’s and plaintiffs’ proposed jury instructions in the underlying criminal case.) Although the Angs’ counsel “readily agree [d]” to the court’s response to the jurors’ question, the Angs now contend that the trial court should have instructed the jury on the elements of each of the charged crimes. Id. at 3823.
¶17 This issue was not adequately raised. In their opening brief below, none of the Angs’ six assignments of error mentioned this alleged deficiency in the jury instructions, nor did any of their seven “issues pertaining to the assignments of error” address the trial court’s failure to instruct the jury on the elements of the underlying criminal charges. RAP 10.3(a)(3). While the Angs’ fifth issue was whether it was “error in the legal malpractice trial to give *487the jury no instructions as to how to determine the plaintiffs’ ‘innocence,’ ” the issue was tied to the first two assignments of error and therefore pertained to the definition of the innocence requirement in Falkner (that is, whether “innocence” meant actual or legal innocence). Br. of Appellants at 3. In any case, the Angs’ brief contained no argument or citation to authority on the question of whether, in light of the jury’s access to the proposed instructions from the criminal trial, jury instruction 13 was adequate. See State v. Olson, 126 Wn.2d 315, 321, 893 P.2d 629 (1995) (approving “proposition that when an appellant fails to raise an issue in the assignments of error, in violation of RAP 10.3(a)(3), and fails to present any argument on the issue or provide any legal citation, an appellate court will not consider the merits of that issue”). The Angs’ incidental allusion (in a footnote in their opening brief) to the absence of “standard criminal law instructions” is inadequate to satisfy RAP 10.3(a)(3). See Br. of Appellants at 29 n.5.
CONCLUSION
¶18 We conclude that, as plaintiffs in a criminal malpractice action, the Angs were properly required to prove by a preponderance of the evidence that they were actually innocent of the underlying criminal charges. We find no persuasive reasons for this court to follow the minority position and shift the burden to the defendant attorneys to prove that their former clients were actually guilty of the charged crimes. Finally, in light of RAP 10.3(a)(3) and prior precedent, which require an appellant to make “separate concise” assignments of error, tie those errors to legal issues, and argue those issues with some citation to authority, we decline to review the Angs’ challenge to jury instruction 13. We affirm the Court of Appeals.
C. Johnson, Madsen, Bridge, and Fairhurst, JJ., concur.The phrase “criminal malpractice” has been widely adopted to denote ‘legal malpractice in the course of defending a client accused of crime.” Otto M. Kaus & Ronald E. Mallen, The Misguiding Hand of Counsel — Reflections on “Criminal Malpractice,” 21 UCLA L. Rev. 1191, 1191 n.2 (1974).
Jury Instruction 12, Br. of Appellants, App. 3 (emphasis added). The jury instructions were not included among the clerk’s papers.
A number of jurisdictions “have imposed appellate, post conviction, or habeas relief, dependent upon attorney error, as a predicate to recovery in a criminal malpractice action, when the claim is based on an alleged deficiency for which appellate, post conviction, or habeas relief would be available.” Berringer v. Steele, 133 Md. App. 442, 758 A.2d 574, 597 (2000). See, e.g., Shaw v. State, 816 P.2d 1358, 1360 (Alaska 1991) (Shaw I); Stevens v. Bispham, 316 Or. 221, 851 P.2d 556, 566 (1993) ; Heck v. Humphrey, 512 U.S. 477, 486-87,114 S. Ct. 2364,129 L. Ed. 2d 383 (1994) ; Morgano v. Smith, 110 Nev. 1025, 879 P.2d 735, 737 (1994); Peeler v. Hughes & Luce, 38 Tex. Sup. Ct. J. 1117, 909 S.W.2d 494, 495 (1995); Adkins v. Dixon, 253 Va. 275, 482 S.E.2d 797, 801 (1997); Steele v. Kehoe, 24 Fla. L. Weekly S237, 747 So. 2d 931, 933 (1999); Coscia v. McKenna & Cuneo, 25 Cal. 4th 1194, 25 P.3d 670, 674-75, 108 Cal. Rptr. 2d 471 (2001); Canaan v. Bartee, 276 Kan. 116, 72 P.3d 911, 916-21, cert. denied, 540 U.S. 1090 (2003).
Falkner, 108 Wn. App. at 123 (emphasis added). Many jurisdictions have imposed an actual innocence requirement. See, e.g., State ex rel. O’Blennis v. Adolf, 691 S.W.2d 498, 503 (Mo. Ct. App. 1985); Carmel v. Lunney, 70 N.Y.2d 169, 511 N.E.2d 1126, 1128, 518 N.Y.S.2d 605 (1987); Glenn v. Aiken, 409 Mass. 699, 569 N.E.2d 783, 785-88 (1991); Shaw II, 861 P.2d at 572; Bailey v. Tucker, 533 Pa. 237, 621 A.2d 108, 113 (1993); Wiley, 966 P.2d at 991; Mahoney v. Shaheen, Cappiello, Stein & Gordon, P.A., 143 N.H. 491, 727 A.2d 996, 998-99 (1999); Rodriguez v. Nielsen, 259 Neb. 264, 609 N.W.2d 368, 374-75 (2000); Griffin v. Goldenhersh, 323 Ill. App. 3d 398, 752 N.E.2d 1232, 1238, 257 Ill. Dec. 52 (2001); Schreiber v. Rowe, 27 Fla. L. Weekly S248, 814 So. 2d 396, 399 (2002); Hicks v. Nunnery, 2002 WI App 87, 253 Wis. 2d 721, 643 N.W.2d 809, 823.