In this appeal defendant brings forth assignments of error relating to the trial court’s refusal to: dismiss the charge of first degree murder for insufficient evidence, suppress defendant’s incriminating statements, permit cross-examination of several witnesses on their motivation for hiring a private prosecutor. He also presents assignments relating to portions of the trial judge’s substantive instructions to the jury and his contention that he suffered from ineffective assistance of counsel. After careful examination of each assignment of error we conclude that defendant’s trial was free from prejudicial error.
The state’s evidence tends to show the following: In the Spring of 1980 defendant was a thirty-six-year-old man who had experienced psychiatric problems and treatment over a period of *112years. In 1976 he had been involved in a commitment proceeding for threatening to kill his father with a knife. He had expressed his belief that his father was trying to poison him a number of times over a span of four to five years. In May of 1980 he told his sister, Sylvia, that as long as his father was alive “he’d never have peace.”
On 10 June 1980 defendant arrived at his father’s residence about 8:00 a.m., while his father was cooking breakfast and his sister, Sharon, was preparing for work. Defendant, rather than enter the residence, went to a shed on the property and ate some food he had purchased at a local restaurant. While in the shed he took an old rifle with the stock removed, loaded it with a single cartridge, and tucked the gun under his belt in the front of his pants. A jacket covered the gun from view. He entered the trailer, remaining in a back bedroom where he was heard but not seen by Sharon before she left for work. He then went into the kitchen where his father was preparing breakfast and told his father he wished to speak with him. His father, sixty-seven years old, but somewhat larger than defendant, spotted the gun and “grabbed for it or grabbed at” defendant. Defendant pulled away. His father grabbed him again. Defendant then reached for the gun, turned, and shot his father in the forehead from a distance of one foot. Defendant left the residence and drove to his brother’s home. Because his brother was not at home, he waited briefly, then decided to drive to South Carolina to help Sylvia, who was in the process of moving.
Sharon returned home shortly after 11:00 a.m. and discovered her father's body on the floor next to the kitchen table. The breakfast utensils were on the table and pans were still on the burners of the stove.
No one other than the deceased and defendant witnessed the shooting; thus the state relied on statements made by defendant to police officers and family members. Defendant met Sylvia in Dillon, South Carolina, and was subsequently detained by the Dillon County Sheriffs Department. About 7:30 p.m. defendant was questioned by two officers of the Mecklenburg County Police Department. After being informed of his Miranda rights, he waived his right to counsel, and gave a statement of his activities that day. During the course of questioning by the officers he told *113them that he had gotten the firearm from the shed because some communists, including his father, had been causing trouble in his father’s trailer park, and because his father had previously attempted to poison him. He also complained to the officers that a laser light was coming through the window of the conference room where he was being questioned, but neither officer could see any light.
In a pre-trial psychiatric evaluation defendant was found competent to stand trial. He presented no evidence at trial.
I
Defendant assigns as error the submission of first degree murder to the jury, contending that the evidence, when viewed most favorably to the state, was insufficient to constitute first degree murder. We disagree.
[1] First degree murder is the unlawful killing of a human being with malice, premeditation and deliberation. State v. Davis, 289 N.C. 500, 223 S.E. 2d 296, death sentence vacated, 429 U.S. 809 (1976); G.S. 14-17 (Cum. Supp. 1979). Generally, premeditation and deliberation must be proved by circumstantial evidence because they “are not susceptible of proof by direct evidence.” State v. Love, 296 N.C. 194, 203, 250 S.E. 2d 220, 226-27 (1978). Premeditation means that defendant formed the specific intent to kill the victim for some period of time, however short, before the actual killing. Deliberation means that the intent to kill was formed while defendant was in a cool state of blood and not under the influence of a violent passion suddenly aroused by sufficient provocation. State v. Biggs, 292 N.C. 328, 337, 233 S.E. 2d 512, 517 (1977); State v. Hamby, 276 N.C. 674, 678, 174 S.E. 2d 385, 387 (1970), death sentence vacated, 408 U.S. 937 (1972). The term “cool state of blood” does not, in the context of determining the existence of deliberation, mean “an absence of passion and emotion. . . . ‘[Although there may have been time for deliberation, if the purpose to kill was formed and immediately executed in a passion, especially if the passion was aroused by a recent provocation or by mutual combat, the murder is not deliberate and premeditated. However, passion does not always reduce the crime since a man may deliberate, may premeditate, and may intend to kill after premeditation and deliberation, although prompted and to a large extent controlled by passion at the time. If the design *114to kill was formed with deliberation and premeditation, it is immaterial that defendant was in a passion or excited when the design was carried into effect.’ ” State v. Faust, 254 N.C. 101, 108, 118 S.E. 2d 769, 773, cert. denied, 368 U.S. 851 (1961), quoting 40 C.J.S., Homicide, s. 33(d), pp. 889, 890. Thus a killing committed during the course of a quarrel or scuffle may yet constitute first degree murder provided the defendant formed the intent to kill in a cool state of blood before the quarrel or scuffle began and the killing during the quarrel was the product of this earlier formed intent. See State v. French, 225 N.C. 276, 34 S.E. 2d 157 (1945). If, however, the killing was the product of a specific intent to kill formed under the influence of the provocation of the quarrel or struggle itself, then there would be no deliberation and hence no murder in the first degree. Id.
The critical question for the jury in this case was whether “defendant did indeed deliberate, as distinguished from premeditate, the killing or did he form the intent to kill during a sudden passion provoked by the deceased [himself] which precluded any such deliberation.” State v. Patterson, 288 N.C. 553, 575, 220 S.E. 2d 600, 616 (1975) (Exum, J., dissenting), death sentence vacated, 428 U.S. 904 (1976). Factors the jury may consider in determining the existence of premeditation and deliberation include: “[CJonduct qnd statements of the defendant both before and after the killing, State v. Johnson, 294 N.C. 288, 239 S.E. 2d 829 (1978), and . . . [T]hreats made against the deceased by the defendant, State v. Stewart, 292 N.C. 219, 232 S.E. 2d 443 (1977).” State v. Potter, 295 N.C. 126, 130-31, 244 S.E. 2d 397, 401 (1978).
[2] In the case at bar all the evidence showed that the killing occurred after defendant and his father had engaged in a struggle and his father had twice “grabbed” defendant. There was also, however, plenary evidence from which the jury could reasonably infer that defendant had formed in a cool state of blood, the specific intent to kill his father well before the struggle actually occurred, and that the killing itself was the product of this earlier formed specific intent to kill rather than an intent formed under the influence of the provocation of the struggle itself.
This evidence in the light most favorable to the state was: Defendant had repeatedly told his siblings that his father was trying to poison him. He had threatened to kill his father on at least one previous occasion. As recently as one month before the killing *115he told his sister “he’d never have peace” as long as his father was alive. On the day of the killing defendant entered a shed on his father’s property, loaded a rifle, and tucked it under his belt where it was hidden by his jacket. He then entered his father’s home, but did not confront his father until his sister had gone to work. His father was unarmed and aware of previous threats made by defendant against him. The only struggle resulted from the deceased’s efforts to disarm defendant. After the shooting defendant acted dispassionately. He drove to his brother’s home, but when he discovered his brother was not at home he decided to drive to South Carolina to help his sister move. When questioned by police officers in Dillon, South Carolina, later that day, defendant coherently and calmly related his actions of that day. He also told them that he carried a gun into his father’s home because his father had attempted to poison him previously and because his father was involved in communist activity in the area.
There was, therefore, no error in denying defendant’s motion to dismiss the charge of first degree murder for insufficiency of the evidence.
II
[3] Defendant next assigns as error the refusal of the trial court to suppress his confession to police officers. Defendant argues he lacked sufficient mental capacity to competently and voluntarily confess at the time he was questioned by officers. He seeks to invoke the rule of Blackburn v. Alabama, 361 U.S. 199 (1960), and State v. Ross, 297 N.C. 137, 254 S.E. 2d 10 (1979), which held that an extra-judicial confession made while a defendant is mentally incompetent must be excluded at trial.
The indicia of incompetency found in Blackburn v. Alabama, supra, and State v. Ross, supra, are significantly different in kind and degree from those found in the present case. The defendant in Blackburn confessed shortly after a crime committed during an unauthorized absence from a Veterans Administration Hospital. He had been diagnosed as schizophrenic and classified as 100 percent incompetent. It was not until four years after his confession that he was declared competent to stand trial. His confession was obtained after eight or nine hours of interrogation in a tiny room with as many as three officers present. Blackburn v. Alabama, supra, 361 U.S. at 200-04.
*116In Ross, the incident and confession at issue occurred shortly after defendant had been involuntarily committed to John Umstead Hospital and subsequently released to his brother’s care. Three days before the crime and confession defendant had been tentatively diagnosed as schizophrenic and given medication. His behavior surrounding the incident for which he was charged was bizarre and three days after his confession defendant was diagnosed as suffering from “chronic, undifferentiated schizophrenia.” State v. Ross, supra, 297 N.C. at 138-42, 254 S.E. 2d at 12-13.
Defendant in this case, however, had presented significantly less compelling indicia of his incompetency. Although he had experienced psychiatric problems in the past and apparently entertained delusions about his father, he was able to function independently of supervision by medical personnel and family members in the weeks prior to the killing and the confession. He was found competent to stand trial after a psychiatric evaluation conducted shortly after his arrest. The trial court made factual findings following a voir dire hearing, concluding that defendant was informed of his Miranda rights and appeared to understand them. The court further found that defendant appeared to be coherent at the time of questioning and not under the influence of drugs other than prescribed medication. The questioning itself was conducted in a well-lighted conference room in less than two hours. Defendant’s various statements during the questioning and afterwards were consistent. Thus, there was ample evidence to support the trial court’s conclusion that defendant’s statements to officers “were made freely and voluntarily and understanding^.”
Ill
[4] Defendant’s next assignment of error relates to the refusal of the trial court to allow cross-examination of defendant’s siblings concerning their motives for hiring a private prosecutor. Several of defendant’s brothers and sisters, including four who testified for the state at trial, hired a private prosecutor to represent the family. He aided in preparation and sat with the state’s prosecutor at trial, but did not examine or cross-examine witnesses. Defense counsel was allowed to ask each of the testifying brothers and sisters whether they were among the family members who had employed private counsel, but was not allowed to pursue the questioning further.
*117Thus this case is distinguishable from prior cases in which this Court held it to be error to prevent any questioning at all on whether the witness had hired a private prosecutor. See, e.g., State v. White, 286 N.C. 395, 405-06, 211 S.E. 2d 445, 451 (1975). In the instant case the testifying family members admitted that the family was represented by a private prosecutor, thus the jury could infer the witnesses’ biases from this information. Although the trial court characterized such employment as not unusual to one juror who questioned the arrangement, this comment did not remove the fact as indicative of interest in the case from the jury’s consideration.
Defendant argues that the sibling witnesses had a pecuniary motive for hiring the private prosecutor and this should have been put before the jury. He contends they hoped to inherit a greater portion of their father’s estate if defendant were to be disqualified as an heir because of a conviction for his father’s murder, see G.S. 31A-3 et seq., and that he should have been allowed to cross-examine them about this possible source of bias. Defendant’s difficulty is that he made no record of what the witnesses would have testified to in this regard, so we have no basis for determining whether defendant was prejudiced by the trial court’s refusal to allow further cross-examination on the issue. The failure to record the witnesses’ excluded response precludes appellate review of its admissibility. See, e.g., State v. Curry, 288 N.C. 660, 220 S.E. 2d 545 (1975).
We note further that defendant could have read the statutes relating to this issue to the jury and argued the bias which these statutes might have engendered in the sibling witnesses. G.S. 84-14; State v. Jones, 296 N.C. 495, 251 S.E. 2d 425 (1979); State v. McMorris, 290 N.C. 286, 225 S.E. 2d 553 (1976). The witnesses’ admission of bias is not a prerequisite for this kind of argument. Thus, we overrule this assignment of error.
IV
[5] Defendant further assigns as error the admission of his brothers’ testimony about statements made by defendant to them. Defendant’s brothers were among the family members who employed a private prosecutor to represent the family in defendant’s prosecution. Defendant argues that his brothers were tantamount to officers of the state because they had employed a *118private prosecutor; thus statements to them were discoverable under G.S. 15A-903(a)(2).2 He further argues that the state failed to supply these statements pursuant to defendant’s request for discovery and this failure renders their admission prejudicial error.
There are several reasons why these contentions are without merit. This Court held in State v. Crews, 296 N.C. 607, 619-20, 252 S.E. 2d 745, 753-54 (1979), that only statements made by defendant to agents of the government are discoverable. We doubt that the mere employment of a private prosecutor makes one an agent of the state for the purposes of G.S. 15A-903(a)(2), but that question need not be decided in this case because the prosecutor apparently complied with the discovery request. Both before and during the voir dire which preceded jury selection, the prosecutor put defendant’s counsel on notice of statements defendant had made to his brothers. The prosecutor stated that he “was generally familiar with the fact that some family members had talked to the [defendant,” but it was not until the night before the hearing that he knew the details of those statements. Thus, the state apparently satisfied its continuing duty to disclose under G.S. 15A-907.3 Defendant had an opportunity to call the brothers for questioning at the voir dire, but failed to do so.
Assuming arguendo that the state did fail to meet its obligation to disclose, defendant made no motions for relief under G.S. *11915A-910,4 nor did he even object to the testimony of one brother at trial. Finally, the decision whether to admit evidence which was not disclosed during discovery is discretionary with the trial court. State v. Braxton, 294 N.C. 446, 472, 242 S.E. 2d 769, 784-85 (1978); State v. Thomas, 291 N.C. 687, 231 S.E. 2d 585 (1977). Absent abuse of discretion, and none is present here, the trial court’s decision is not subject to appellate review. See, e.g., 1 N.C. Index 3d, Appeal and Error § 54, p. 330 (1977).
V
[6] Defendant next asserts that the trial court committed reversible error when he defined involuntary manslaughter as “the unlawful killing of a human being by an unlawful act not amounting to a felony, or an act done in a criminally negligent way.” Defendant contends the court should have said “unintentional killing” rather than “unlawful killing.” We agree that the accepted definition of involuntary manslaughter is the unintentional killing of a human being by an unlawful act not amounting to a felony nor naturally dangerous to human life, or an act or omission which is criminally negligent. State v. Redfern, 291 N.C. 319, 230 S.E. 2d 152 (1976); N.C. P.I. —Crim. 206.11. Although involuntary manslaughter is an unlawful killing, like all homicides, the unintentional nature of the killing is that characteristic which in the ordinary case best distinguishes it from the other homicides.5 We are satisfied, however, that this deviation from the accepted definition by the trial judge was not prejudicial in this case. First, the trial court explained the elements of involuntary manslaughter in two portions of his jury charge. It was only in the first that he used the term “unlawful killing.” In the second he used the accepted definition. Then in his final mandate he appropriately ap*120plied the correct legal standard in charging on this crime. Because the use of the term “unlawful killing” was not altogether incorrect and because of these later correct instructions on the point we conclude no prejudice to defendant resulted. See State v. Wells, 290 N.C. 485, 226 S.E. 2d 325 (1976); State v. Gray, 268 N.C. 69, 150 S.E. 2d 1 (1966), cert. denied, 386 U.S. 911 (1967). Second, the record reveals no basis for submitting the alternative charge of involuntary manslaughter to the jury. There is no evidence that the shooting in this case was unintentional. See State v. Faust, supra, 254 N.C. at 112-13, 118 S.E. 2d at 776-77; State v. Cope, 204 N.C. 28, 31, 167 S.E. 456, 458 (1933). Because, however, defendant was convicted of first degree murder, he was not prejudiced by the erroneous submission of involuntary manslaughter. Compare State v. Wilkerson, 295 N.C. 559, 247 S.E. 2d 905 (1978), with State v. Ray, 299 N.C. 151, 261 S.E. 2d 789 (1980) (prejudicial error to submit lesser offense of involuntary manslaughter when no evidence to support charge and reasonable possibility of acquittal without it).
VI
[7] The final issue raised by defendant is whether he was afforded effective assistance of counsel at trial. Defendant points to the failure of trial counsel to renew his motion to dismiss at the close of all the evidence and to introduce evidence in defendant’s behalf. Neither of these omissions by trial counsel on this record constitute ineffective representation.
Defendant’s right to assistance of counsel in a non-capital felony prosecution is guaranteed by the Sixth Amendment to the United States Constitution, made applicable to the states by the Fourteenth Amendment, Gideon v. Wainwright, 372 U.S. 335 (1963), and Article I, Sections 19 and 23 of the North Carolina Constitution. The test of effective assistance of counsel has never been definitively stated by the United States Supreme Court; however, that Court has evaluated advice given a defendant who pleaded guilty by determining whether it was “within the range of competence demanded of attorneys in criminal cases.” McMann v. Richardson, 397 U.S. 759, 771 (1970). Several courts, including this one, have looked “to the ABA Standards Relating to the Defense Function as a ‘reliable guide for determining the responsibilities of defense counsel.’ Marzullo v. Maryland, 561 F. 2d 540, *121547 (4th Cir. 1977), cert. denied, 435 U.S. 1011, 56 L.Ed. 2d 394, 98 S.Ct. 1885 (1978).” State v. Milano, 297 N.C. 485, 495, 256 S.E. 2d 154, 159 (1979).
The test of effective assistance has been expressed two ways by this Court. Traditionally, the formulation has been whether “the attorney’s representation is so lacking that the trial has become a farce and a mockery of justice.” State v. Sneed, 284 N.C. 606, 612, 201 S.E. 2d 867, 871 (1974). Recently, however, we employed the McMann standard and the ABA Standards without mention of the “farce and mockery” standard6 in reviewing an ineffective assistance of counsel claim in a case in which the defendant had not pleaded guilty. State v. Milano, supra, 297 N.C. at 494, 256 S.E. 2d at 159. Under either of these tests defendant has failed to meet the “stringent standard of proof on the question of whether an accused has been denied Constitutionally effective representation.” State v. Sneed, supra, 284 N.C. at 613, 201 S.E. 2d at 871-72.
The failure to renew a motion to dismiss made at the close of all the evidence does not preclude appellate review of the sufficiency of all the evidence in a criminal case. G.S. 15A-1227(d). Furthermore, defendant presented no evidence so a renewal of the motion would have been futile. The failure of defense counsel to renew his motion to dismiss does not constitute ineffective assistance of counsel.
[8] Defendant next attacks the decision not to put forth any evidence in his defense at trial. The decision not to testify at trial was clearly defendant’s own. He made a sworn statement at trial, in response to the court’s questioning, that he understood he had the right to testify but preferred not to do so.
Defendant also asserts it was ineffective representation for his counsel to fail to offer any psychiatric testimony about his mental condition. On the basis of this record we cannot say that the failure to introduce psychiatric testimony was “so flagrant *122that a court can conclude that it resulted from neglect or ignorance rather than from informed, professional deliberation.” Marzullo v. Maryland, supra, 561 F. 2d at 544. Defense counsel requested and received a psychiatric determination of defendant’s competency to stand trial. The record shows the court ordered as part of that report an evaluation of defendant’s mental state on 10 June 1980. Absent some showing that evidence of defendant’s insanity was available, or by the exercise of due diligence could have been developed by counsel and presented in defendant’s behalf, we cannot conclude that defendant suffered from ineffective assistance of counsel because no such evidence was offered.7
Defendant having failed to show prejudicial error, we find in the verdict and judgment of the trial court
No error.