A jury convicted Johnny Lee Adams of malice murder in the beating death of Dorothea Daniels.1 He appeals, contending that the malice murder statute is unconstitutional because it fails to give notice that the offense can be committed by assaulting a person with a large rock. Because Adams failed to raise this issue in a timely manner, it is waived. His remaining enumerations of error have no merit and we affirm.
1. The evidence at trial showed that Adams and Daniels often met after work to do drugs and have sex. On the night of the murder, they went to a wooded area behind a strip mall, drank beer, and engaged in sex on a panel board lying on the ground. After Daniels questioned Adams about his seeing another woman, Adams became angry and beat her severely with a rock around the head and face. Daniels died as a result of the wounds inflicted by Adams.
After reviewing the evidence in the light most favorable to the jury’s determination of guilt, we conclude that a rational trier of fact could have found Adams guilty of the crimes charged.2
2. Adams asserts that the statutes under which he was convicted, OCGA §§ 16-5-1, 16-5-1 (c) and 16-5-21 (a), are unconstitutionally vague because they do not give adequate notice that malice murder, felony murder, and aggravated battery can be committed by assaulting a person with a large rock. We need not address the merits, if any, of this challenge, because Adams failed to raise it until the motion for new trial.3
3. Adams raises several enumerations of error with regard to the hearing to determine his competency to stand trial. First, Adams challenges the sufficiency of the evidence. At a competency hearing, the defendant bears the burden of proving incompetency by a preponderance of the evidence.4 “A criminal defendant is competent to stand trial if he is capable of understanding the nature and object of the *868proceedings and is capable of assisting his attorney with his defense.”5 There was ample evidence showing that Adams met this standard. Additionally, the expert testimony was consistent in showing that Adams was exaggerating his claimed symptoms of psychosis and diminished intellectual function. Therefore, the evidence supports the special jury’s finding of competency.
Second, Adams contends that it was error to prevent Sandra Mullins, a licensed clinical social worker, from testifying as an expert regarding opinions formed during her evaluation of Adams. Mullins had evaluated Adams and was prepared to testify that she made a provisional diagnosis of paranoid-type schizophrenia and that she had formed an opinion of his level of intellectual functioning. The trial court excluded this testimony because whether Adams had a mental disorder was a medical opinion, only doctors can give medical opinions, and Mullins was not a doctor. This ruling was error.
Mullins’s testimony detailed her educational background and experience in evaluating the mental condition of patients. She testified that she is licensed as a clinical social worker by the Composite Board of the State of Georgia, that her license allows her to interview patients and make diagnostic impressions using the Diagnostic Statistical Manual IV,6 that she has the authority to commit a person against his will, and that she had years of experience in performing psycho-social assessments of patients to determine their mental status. This testimony was sufficient to allow her to give expert testimony regarding her professional evaluation of Adams.7 The fact that she did not hold a medical degree goes only to the weight the jury may give her testimony.8
Nevertheless, we conclude that the error was harmless for several reasons: Mullins’s testimony would have been cumulative of a psychiatrist called by Adams; the expert testimony showed that even with a diagnosis of schizophrenia, a defendant could be competent to stand trial; and all of the experts agreed that Adams was exaggerating his symptoms.
Third, Adams contends that it was error to compel a defense expert to produce a written report for the State. The record shows *869only that the State requested the report from the witness and the witness provided it directly to the State, apparently without consulting defense counsel. Under these circumstances, we find no reversible error.9
4. Adams contends that the trial court erred in admitting his custodial statements because he is mentally retarded, uneducated, and illiterate. The evidence at the Jackson-Denno10 hearing, however, demonstrated that Adams was advised of his rights several times, acknowledged that he understood them, and waived them.
He also challenges the statements’ admission on the ground that they were the fruit of an unlawful arrest and detention because the police lacked probable cause to arrest him. The record, however, shows that probable cause existed.
5. Adams raises several challenges to the jury instructions. However, a review of the instructions as a whole demonstrates no reversible error.
6. Adams contends that the failure to preserve the panel board on which the victim was found constitutes a denial of due process. To determine whether the failure to preserve evidence constitutes a denial of due process, we must consider whether the evidence was material and whether police acted in bad faith.* 11 A sheriff’s deputy testified that the sheriff’s department had no ability to transport or store the board because of its size and its contamination with formaldehyde. He also testified that the fire department was supposed to take charge of the board, but apparently did not. Additionally, Adams has not shown that the board was material or contained evidence that would have exonerated him. Therefore, we conclude that the failure to preserve this board did not constitute a denial of due process.
Judgment affirmed.
All the Justices concur, except Benham, Carley and Thompson, JJ, who concur specially.The crime occurred May 5, 1998. A grand jury indicted Adams on September 9, 1998, and on September 29, 2000, a special jury found him competent to stand trial. Following a jury trial on June 25-27, 2001, Adams was convicted of malice murder, felony murder, and two counts of aggravated battery; he was acquitted of rape. The trial court sentenced Adams to life imprisonment for malice murder and imposed two 20-year sentences for aggravated battery, to run concurrently with each other and consecutive to the life sentence. Adams filed a motion for new trial on August 6, 2001, which the trial court denied on December 21, 2001. Adams filed a notice of appeal on January 17, 2002, and the case was docketed in this Court on March 18, 2002, and submitted for decision without oral argument on May 13, 2002.
Jackson v. Virginia, 443 U. S. 307 (99 SC 2781, 61 LE2d 560) (1979).
Hardeman v. State, 272 Ga. 361 (529 SE2d 368) (2000).
Stowe v. State, 272 Ga. 866, 867 (536 SE2d 506) (2000).
Stripling v. State, 261 Ga. 1, 2 (401 SE2d 500) (1991).
OCGA § 43-10A-12 (c) provides that licensed clinical social workers may “provide psychosocial evaluation ... to determine the nature of an individual’s mental, cognitive, emotional, behavioral, and interpersonal problems or conditions.”
Carr v. State, 267 Ga. 701, 708 (482 SE2d 314) (1997) (“[qlualification as an expert requires that the witness be educated in a particular skill or profession, or derive knowledge from experience”). Dicta to the contrary in Ellis v. State, 168 Ga. App. 757 (309 SE2d 924) (1983), which involved a police officer giving testimony regarding paranoid behavior, is unpersuasive.
McCoy v. State, 237 Ga. 118 (227 SE2d 18) (1976) (jury considers expert’s credentials and gives weight as it deems appropriate).
Compare Johnson v. State, 265 Ga. 833 (463 SE2d 123) (1995) (error to require defense experts to reduce reports to writing and supply to State).
378 U. S. 368 (84 SC 1774, 12 LE2d 908) (1964).
Walker v. State, 264 Ga. 676, 680 (449 SE2d 845) (1994).