§1. Testimony.
The most common form of evidence admitted in a criminal proceeding is testimony. Testimony is generally defined as a response that a competent witness gives under oath or affirmation for the purpose of proving some fact. See Evid. C. §§701, 710; Testimony, Black's Law Dictionary (11th ed. 2019). The response elicited from the witness can be verbal or nonverbal. See People v. Miranda (2d Dist.2011) 199 Cal.App.4th 1403, 1430-31 (Mosk, J., concurring).
§1.1. Foundational requirements. For a witness to testify, the witness must (1) be competent to testify and (2) have personal knowledge of the subject matter of her testimony. Evid. C. §§701, 702.
1. Competency.
(1) Generally. As a general rule, every person is presumed competent to testify. Evid. C. §700; People v. Willard (2d Dist.1983) 155 Cal.App.3d 237, 239. See "Challenging competency,' ch. 2, §1.2.1. To be considered competent and qualified to be a witness, a person must (1) be capable of expressing herself satisfactorily so as to be fully understood and (2) understand the duty to tell the truth. Evid. C. §701(a). Thus, the age or mental impairment of a witness will not automatically disqualify a person from testifying as long as the witness possesses the capacity to communicate and comprehends the duty to tell the truth. See, e.g., People v. Sanchez (2019) 7 Cal.5th 14, 30-31 (seven-year-old child was found competent to testify about his eyewitness account of events surrounding murders; although he initially testified that he did not know difference between truth and lies, he later demonstrated his understanding and acknowledged importance of telling truth while sitting in witness chair); People v. Lopez (2018) 5 Cal.5th 339, 351-52 (six-year-old child was found competent to testify about her eyewitness account of child abuse); People v. Dennis (1998) 17 Cal.4th 468, 524-25 (eight-year-old child was found competent to testify about her eyewitness account of events surrounding her mother's murder); People v. Giron-Chamul (1st Dist.2016) 245 Cal.App.4th 932, 960-61 (five-year-old child was competent to testify about her sexual abuse); People v. Gipson (6th Dist.2004) 117 Cal.App.4th 1065, 1071-72 (mental disorder did not render witness incapable of communicating; all details relating to his substance abuse and hospitalizations were disclosed to jury for proper credibility assessment).
(a) Capable of being understood. If a witness is incapable of being understood because of a language barrier, the court may appoint an interpreter. 7 Cal. Law Revision Comm'n Rep. (1965) p. 1115; see Evid. C. §752(a). The statute is construed broadly so that if the source of a person's inability to understand is a "physical disability," the appointment of an interpreter will be warranted. 7 Cal. Law Revision Comm'n Rep. (1965) p. 1115.
(b) Capable of understanding duty to tell the truth. Generally, a witness must take an oath or make an affirmation or declaration to testify truthfully...
