While many people may be familiar with the concept of a “burden of proof” utilized in a trial court, less are familiar with the “standards of review” employed in appeals.
In legal terms, an “appeal” is a legal proceeding that is undertaken to have a decision of a lower court or agency reconsidered by a higher authority. In other words, an appeal is the legal process of asking a higher court to modify, confirm, or toss-out the decision of a lower court. Although appeals can involve agencies or administrative bodies, references to appeals most often involve the court system.
When most people picture a courtroom, they typically picture a trial court with lawyers presenting physical evidence and making impassioned arguments in an effort to convince a judge or jury that their version of the facts in a dispute is the correct one. Although, in real life, the proceedings in trial courts aren’t often as dramatic as most people may visualize, they are generally accurate in depicting that trial courts make rulings on issues of fact—for example, whether a defendant actually committed a crime or whether someone was actually injured in a slip and fall. In the context of appeals, a lower court is most often a trial court. When a party involved in a trial or lower court hearing disagrees with a court’s ruling, they may appeal by asking an appellate court to review the disputed ruling.
In contrast to trial courts, appellate courts often review appeals behind closed doors. Additionally, unlike trial courts, appellate courts are generally not concerned with issues of fact but, instead, are concerned with issues of law—for example, whether a specific procedure was followed in carrying out a trial, or whether a court admitted evidence in a trial it wasn’t legally permitted to. Although appeals occasionally include oral arguments—sessions where attorneys involved in the appeal present arguments to, and answer questions from, a panel of judges—appeals are often decided on written briefs submitted by the parties. The United States Supreme Court and the Colorado Court of Appeals are examples of courts with appellate jurisdiction.
In reviewing issues on appeals, appellate courts follow standards of review to help reach a holding on a given issue. Although not the same as a burden of proof, a standard of review is a similar concept in that it is a measurement of the amount of deference a reviewing court will afford to the ruling of the lower court. Where the standard of review is higher, a reviewing court will be less likely to overturn the ruling of a lower court. Although standards of review may differ slightly from court-to-court and state-to-state, most appellate courts apply similar standards to issues involving questions of fact, questions of law, and mixed questions of law and fact.
Some of the more common standards of review include:
A “de novo” standard of review is a low standard in which a reviewing court exercises its own judgment and re-determines a legal issue. In other words, a de novo standards allows a reviewing judge to re-weigh the evidence, second-guess the appointing authority, and arrive at his own decision.  A de novo standard is often used when reviewing a trial court’s conclusions of law.
A “clearly erroneous” standard is a more deferential standard of review that is typically applied by a higher court when reviewing a lower court’s factual findings. A lower court’s finding may be clearly erroneous where such finding has “no support” in the trial court record  or where, even if there is some evidence to support the finding, “the reviewing court is left with the definite and firm conviction that the trial court committed a mistake.” 
Abuse of Discretion
Under an abuse of discretion standard, a lower court’s ruling will not be overturned absent a showing of abuse of discretion. An abuse of discretion standard is one of high deference. An abuse of discretion may be evidenced where a ruling is “manifestly arbitrary, unreasonable, or unfair”  or where a decision is both unreasonable and made “without reference to guiding principles.”  An abuse of discretion standard may be applied in situations where, for example, a trial court’s order granting or denying an expunction is at issue or where a trial court’s order regarding production of a trade secret is at issue.
Other standards of review may include “harmless error,” “plain error,” “substantial evidence,” or an “arbitrary and capricious” standard.
 See, e.g., Dep’t of Corr. v. Stiles,477 P.3d 709 (Colo. 2020).
 See, e.g., People ex rel. A.J.L., 243 P.3d 244 (Colo. 2010).
 See, e.g., Musick v. State, 862 S.W.2d 794 (Tex. App.—El Paso, 1993).
 See, e.g., Harris Group v. Robinson,209 P.3d 1188 (Colo. App. 2009).
 See, e.g., Goode v. Shoukfeh, 943S.W.2d 441 (Tex. 1997).