Appellant's burden must specifically be met if he or she seeks appellate review of the trial court's exclusion of evidence. "Before an appellate court can knowledgeably rule upon an evidentiary issue presented, it must have an adequate record before it to determine if an error was made. For this purpose we are limited to reviewing the matters appearing in the record." In re Mark C. (1992) 7 Cal.App.4th 433, 445 (citation omitted). First, the party seeking admission of evidence must make sure that the trial court issues a ruling on the admissibility of the evidence on the record. Failure to do so waives that issue on appeal. Demps v. San Francisco Housing Auth. (2007) 149 Cal.App.4th 564, 578 (waiver if no ruling on each individual objection to evidence in summary judgment motion); Slauson Partnership v. Ochoa (2003) 112 Cal.App.4th 1005,1014, fn.4 (objections to declarations in opposition to anti-SLAPP motion to strike); Juarez v. Boy Scouts of America, Inc. (2000) 81 Cal.App.4th 377, 398, fn.7 (hearsay objection).

An exception to this rule applies if the appellant made a diligent effort to obtain a trial court ruling on the objection but the trial court refused to rule. City of Long Beach v. Farmers & Merchants Bank of Long Beach (2000) 81 Cal.App.4th 780, 784-785. In City of Long Beach trial counsel made two requests for rulings on evidentiary objections but the trial court refused to rule. The appellate court in City of Long Beach held that "It would have been a fruitless or idle act to have interposed a third oral request for rulings." City of Long Beach, supra.

Next, the appellant must make an offer of proof of the excluded evidence at trial or else he or she waives any argument on appeal or on a new trial motion based on erroneous exclusion of evidence. Heiner v. Kmart Corp. (2000) 84 Cal.App.4th 335, 344. A party waives, or forfeits, their trial court objection by failing to object when an objection could have been, but was not, raised to the trial court by appropriate means. In re S.B. (2004) 32 Cal.4th 1287, 1293. Evid. § 354(a) states that: "A verdict or finding shall not be set aside, nor shall the judgment or decision based thereon be reversed, by reason of the erroneous exclusion of evidence unless...[t]he substance, purpose and relevance of the excluded evidence was made known to the court by the questions asked, an offer of proof, or any other means..." An offer of proof "must consist of material that is admissible, it must be specific in indicating the purpose of the testimony, the name of the witness and the content of the answer to be elicited." Semsch v. Henry Mayo Newhall Memorial Hospital (1985) 171 Cal.App.3d 162, 167.

Dillenbeck v. City of Los Angeles(1968) 69 Cal.2d 472, 476, fn.1, provides an example of a sufficient offer of proof. Dillenbeck involved a wrongful death action brought against the City of Los Angeles arising out of a collision between the decedent's car and a car driven by a police officer in the course of his employment. Dillenbeck, 69 Cal.2d at 474. The trial court excluded current police training bulletins as guidelines on the applicable standard of care. Dillenbeck, 69 Cal.2d at 475-476. The Supreme Court reversed the judgment in the City's favor. Dillenbeck, 69 Cal.2d at 484.

The Court pointed out that the plaintiffs' offer of proof was adequate. The plaintiffs offered the text of the bulletins and the three purposes for which they were offered into evidence: as evidence of the applicable standard of care of a police officer; whether defendant officer failed to comply with these applicable standards; and whether the decedent was contributorily negligent in proceeding despite defendant's use of the car siren, based on the observations in one of the proffered bulletins that a motorist in similar circumstances will not ordinarily hear the siren. Appellant also offered a stipulation with the opposing party that these bulletins were the most recent ones issued by the police department to its officers. Dillenbeck, 69 Cal.2d at 475-476, fn. 1.

There are exceptions to this rule that excuse the failure to make an offer of proof. Evid. § 354(c) does not require an offer of proof for evidence obtained through cross-examination. Tossman v. Newman (1951) 37 Cal.2d 522, 525. The rationale for the exception is that cross-examination is exploratory and it would be unreasonable to require an offer of proof because the attorney often does not know what facts will be elicited. Tossman, supra. However, this exception is itself subject to two exceptions. First, an offer of proof is required when the cross-examination exceeds the scope of direct examination. People v. Foss (2007) 155 Cal.App.4th 113, 127. Second, if the trial court seeks an explanation or its ruling shows that it sees no proper purpose for a line of questioning then counsel must provide an offer of proof to preserve the issue for appeal, for example if a line of questioning appears to be irrelevant. People v. Allen (1986) 42 Cal.3d 1222, 1270, fn. 31.

An offer of proof is also unnecessary if the substance and purpose of the evidence is clear, such as through a motion in limine or pretrial conference order. Evid. § 354(a) ("or any other means"); Delta Dynamics, Inc. v. Arioto (1968) 69 Cal.2d 525, 527-528, fn. 1 (pretrial conference order sufficed to preserve issue for appeal even in absence of adequate offer of proof).

The final exception to the rule requiring a party to make an offer of proof to preserve a trial court exclusion of evidence issue for appeal arises when the trial court?s ruling makes such an offer futile. Evid. § 354(b). One example of such a ruling arises when the trial court excludes an entire class of evidence. The trial court in Pacific Gas & Elec. Co. v. G. W. Thomas Drayage & Rigging Co. (1968) 69 Cal.2d 33 excluded all extrinsic evidence offered to interpret a contract, thereby making futile an offer of proof of the substance and relevance of the proposed parol evidence. Pacific Gas & Elec., supra, 69 Cal.2d at 36, fn.1. Exclusion of all causation testimony from an expert witness based on the propounding party's failure to designate that expert witness on the causation issue likewise made an offer of proof unnecessary. Casteneda v. Bornstein (1995) 36 Cal.App.4th 1818, 1827, disapproved on other grounds in Bonds v. Roy (1999) 20 Cal.4th 140, 149, fn.4. Nor was an offer of proof necessary when the trial court ruled that it would not admit any evidence of specific acts of misconduct to impeach the testimony of the complaining witness. People v. Adams (1988) 198 Cal.App.3d 10, 18-19.

Despite these exceptions, however, prudence dictates making an adequate offer of proof whenever possible to preserve the ruling excluding evidence for appeal.

The exceptions to the rule requiring a party to make an offer of proof in order to preserve an argument that evidence was erroneously excluded in the trial court are limited. They should only be relied upon as a last resort if no adequate offer of proof is made. Those exceptions arise when: an offer of proof would be futile, such as when the trial court excludes an entire class of evidence; when the substance and purpose of the evidence is clear, whether through a motion in limine or pretrial conference order; and when the party elicits the evidence on cross-examination within the scope of direct and the trial court recognizes the proper purpose of the line of questioning.