There are two types of witnesses, lay witnesses and expert witnesses. A lay witness is any witness who can give testimony relevant to an issue in the case. An expert witness is anyone who, through training, education, skill, or experience, has particular knowledge that the average juror would not possess concerning questions of science, skill, trade, or similar areas. Thomas v. State, 290 Ga. 653 (2012); Hubert v. State, 297 Ga. App. 71 (2009).
A lay witness must testify based upon personal knowledge. O.C.G.A. § 24- 6-602. A witness who personally observed the event to which he is testifying may state his impressions drawn from and opinions based upon the facts and circumstances observed by him. Dunn v. State, 291 Ga. 551 (2012). Smith v. State, 290 Ga. 428 (2012). A lay witness is also entitled to give his opinion as to the defendant's behavior so long as it is based on the witness' observation and the witness states the facts upon which the opinion is based. However, a witness generally may not express an opinion on the ultimate issue in the case. Mangrum v. State, 285 Ga. 676 (2009). The ultimate issue is the issue to be decided by the jury (such as whether it was self-defense). A mental disease does not necessarily make a witness incompetent to testify. As long as the witness understands his obligation to tell the truth he is competent to testify. Ellis v. State, 316 Ga. App. 352 (2012); Dorsey v. State, 206 Ga. App. 709 (1992). A witness may refresh his recollection with any document as long as he testifies from his recollection which has been refreshed or can swear positively from the document. Ashmid v. State, 316 Ga. App. 550 (2012).
The requirements for qualification as an expert witness are minimal; generally nothing more is required than evidence that the person has been educated in a particular trade, science, or profession. Formal education is not required. Ashley v. State, 316 Ga. App. 28 (2012). The jury may believe or disbelieve all or any part of the testimony of a witness, lay or expert. Where a witness' qualifications are established, the witness does not need to be formally tendered and accepted as an expert in order to give expert testimony. Wilson v. State, A12A0010; Fielding v. State, 278 Ga. 309 (2004).
The current statute governing the admissibility of expert testimony in criminal cases is OCGA § 24-7-702 Tthe General Assembly repealed former OCGA § 24-7-707 (2013). The evidentiary requirements relating to the admissibility of expert opinion testimony in a criminal case under [former OCGA § 24-7-707 (2013)] are nearly identical to those that applied under the former Evidence Code (OCGA § 24-9-67). Accordingly, it is appropriate to rely . . . on decisions under the old Code. Robinson v. State, 309 Ga. 729, 735 n.2 (848 SE2d 441) (2020); Beard v. State, S23a0906 (December 19, 2023)
An expert witness may testify about opinions based on facts within his knowledge or facts admitted into evidence at trial and presented to the expert in the form of hypothetical questions. Where an expert testifies based on facts within evidence the testimony is admissible even if the expert never went to the scene or observed the facts. Elrod v. State, 316 Ga. App. 491 (2012). However, when the basis of the expert opinion is totally speculative, and not based on any facts, the opinion has no probative value. Cronkie v. State, 317 Ga. App. 57 (2012).
Expert testimony is not necessary where the jury may make their own determination. Walden v. State, 289 Ga. 845 (2011). The judge can exclude expert testimony on the theory of false confessions on the basis that this knowledge is not beyond the ken of the average juror. Riley v. State, 278 Ga. 677 (2004).
When a party wants a person to be considered an expert, the witness is questioned about his background, qualifications, and experience. The attorney seeking to have the witness considered an expert then tenders or submits the witness as an expert. The other side can object to the witness being accepted as an expert or question the witness concerning the witness' qualifications. Although a formal tender of an expert witness is preferred, the lack of a formal tender does not prevent the expert from being treated as an expert as long as the opposing party had the opportunity to cross-examine the expert about his credentials and testimony. Fowler v. State, 294 Ga. App. 864 (2008). The determination of whether to accept or reject an expert witness rests within the sound discretion of the judge Taylor v. State, 261 Ga. 287 (1991).
The judge may also call a court appointed expert. O.C.G.A. § 24-6-614. The State and defense are given the opportunity to cross- examine an expert that the judge calls as a witness. An expert may rely upon the statements of others in forming his opinions. O.C.G.A. §§ 24-6-703 – 24-6-707. However, those opinions should be given weight only to the extent that the statements upon which he relies are proven reliable. An expert witness cannot merely serve as a conduit for hearsay. Humphrey v. Morrow, 289 Ga. 864 (2011).
Expert opinion testimony on issues to be decided by the jury, even the ultimate issue, is admissible where the conclusion is one which the jurors would not ordinarily be able to draw for themselves. Jefferson v. State, 312 Ga. App. 842 (2011); O.C.G.A. § 24-7-704. However, even an expert witness cannot testify that the defendant had the required intent to commit the crime.
An expert may express an opinion as to whether medical or other objective evidence in the case is consistent with the alleged victim's testimony. Hart
v. State, 314 Ga. App. 685 (2012); Ledford v. State, 313 Ga. App. 389 (2011). Whether to believe an expert witness is up to the jury. Stanley v. State, 289 Ga. App. 373 (2008).