KATZ, J.
Following a jury trial, the defendant, Carol Tomasko, was convicted of murder in violation of General Statutes § 53a-54a (a).1 The defendant has appealed2 from the judgment of the trial court sentencing her to fifty years imprisonment. On appeal, the defendant claims that: (1) the evidence was insufficient to prove beyond a reasonable doubt that she intended to kill the [255]*255victim; (2) the trial court improperly refused to instruct the jury on the lesser included offense of criminally negligent homicide in violation of General Statutes § 53a-58;3 and (3) the trial court improperly overruled the defendant’s objection to the introduction into evidence of two tape-recorded conversations between the state’s chief witness and the defendant.4 We affirm the judgment of the trial court.
The jury reasonably could have found the following facts. On September 14, 1981, the defendant lived in Stratford with her husband, the victim, and her daughter, Suzette Meyer. The defendant and the victim shared a history of marital strife. On the night of the murder, the defendant and the victim were arguing because the victim had been arrested for driving an unregistered motor vehicle, and the victim had accused the defendant of having informed the police. In the course of the argument, the defendant threw a beer bottle at the victim, who had been drinking. Meyer, who was sitting at the kitchen table across from the victim, was looking down when she heard a loud noise. When Meyer looked up, she saw that the defendant was standing near the doorway holding a small handgun, and that the victim was slumped in his seat at the kitchen table. The victim died from a single gunshot wound to the back of the head.
Although Meyer did not actually see the defendant pull the trigger, she testified that the defendant had [256]*256been moving around during the course of the argument and, at one point, had entered Meyer’s bedroom. Meyer and the victim’s son both testified that the defendant customarily carried the handgun in her pocketbook, which she normally kept in Meyer’s bedroom.
After the shooting, the defendant held the gun to Meyer’s head and told her to help clean up the blood from the floor. While Meyer was cleaning the floor, the defendant dragged the victim’s body out the back door and into the yard. Meyer then assisted the defendant in lifting the victim’s body into a pickup truck. Thereafter, the defendant, with Meyer as a passenger, began driving the pickup truck through Stratford. Because the truck developed mechanical problems, the defendant drove the truck to the house of her brother, Ellsworth Hull, where the engine stopped running. Hull, who never noticed the victim’s body in the bed of the truck, was unable to jump start the vehicle. Hull then drove Meyer and the defendant home. Meyer never saw the victim’s body again. One week later, Meyer learned that the victim’s body had been found floating in Long Island Sound.
Because Meyer feared for her life as a result of the defendant’s threats, she did not tell the police about the incident until 1992. On September 2, 1992, after reading an article in the local newspaper about the unsolved murder, Meyer told Hull, in whose home she was then living, about the murder. Meyer contacted the police that same day and implicated the defendant. After an investigation in which Meyer assisted the police, the defendant was arrested and charged in a one count information with murder. Additional facts will be presented as needed.
[257]*257I
The defendant’s first claim is that the trial court improperly denied her motion for judgment of acquittal because the evidence was insufficient to prove beyond a reasonable doubt that she had had the specific intent to cause the death of the victim. We disagree.
“In reviewing a sufficiency [of the evidence] claim, we apply a two part test. First, we construe the evidence in the light most favorable to sustaining the verdict. Second, we determine whether upon the facts so construed and the inferences reasonably drawn therefrom the jury reasonably could have concluded that the cumulative force of the evidence established guilt beyond a reasonable doubt. . . . State v. Greenfield, 228 Conn. 62, 76, 634 A.2d 879 (1993). The specific intent to kill is an essential element of the crime of murder. To act intentionally, the defendant must have had the conscious objective to cause the death of the victim. General Statutes § 53a-3 (11). . . . State v. Raguseo, 225 Conn. 114, 120, 622 A.2d 519 (1993). Intent is generally proven by circumstantial evidence because direct evidence of the accused’s state of mind is rarely available. State v. Greenfield, supra, 77. Therefore, intent is often inferred from conduct; id., 76; and from the cumulative effect of the circumstantial evidence and the rational inferences drawn therefrom. State v. Raguseo, supra, 119.” (Internal quotation marks omitted.) State v. Mejia, 233 Conn. 215, 223, 658 A.2d 571 (1995). “Furthermore, [i]ntent to cause death may be inferred from the type of weapon used, the manner in which it was used, the type of wound inflicted and the events leading to and immediately following the death. . . . State v. Raguseo, supra, 120.” (Internal quotation marks omitted.) State v. Mejia, supra, 224. “This does not require that each subordinate conclusion established by or inferred from evidence, or even from other inferences, be proved beyond a reasonable doubt [258]*258because this court has held that a jury’s factual inferences that support a guilty verdict need only be reasonable. State v. Crafts, 226 Conn. 237, 244, 627 A.2d 877 (1993). Nevertheless, because intent to cause the death of a person is an element of the crime; State v. Raguseo, supra, 120; that intent must be proven beyond a reasonable doubt. Patterson v. New York, 432 U.S. 197, 204, 97 S. Ct. 2319, 53 L. Ed. 2d 281 (1977); In re Winship, 397 U.S. 358, 364, 90 S. Ct. 1068, 25 L. Ed. 2d 368 (1970).” (Internal quotation marks omitted.) State v. Mejia, supra, 223-24.
“We do not sit as a thirteenth juror who may cast a vote against the verdict based upon our feeling that some doubt of guilt is shown by the cold printed record. . . . Rather, we must defer to the jury’s assessment of the credibility of the witnesses based on its firsthand observation of their conduct, demeanor and attitude. . . . State v. Henning, 220 Conn. 417, 420, 599 A.2d 1065 (1991). This court cannot substitute its own judgment for that of the jury if there is sufficient evidence to support the jury’s verdict. . . . State v. Hart, 198 Conn. 424, 427, 503 A.2d 588 (1986).” (Internal quotation marks omitted.) State v. Mejia, supra, 233 Conn. 224.
The evidence presented at the defendant’s trial was sufficient to support the jury’s finding beyond a reasonable doubt that she had intended to kill the victim. Meyer testified that the defendant and the victim had had a history of marital conflicts. On the night of the shooting, the victim had accused the defendant of telling the police that he had been operating an unregistered vehicle. An argument ensued and the defendant threw a beer bottle at the victim. Although Meyer did not see the defendant leave the kitchen, she did testify that the defendant customarily carried her gun in her pocketbook, which she normally left in Meyer’s bedroom. Therefore, the jury could have inferred that the defendant had left the kitchen to retrieve her gun before [259]*259shooting the victim in the back of the head. We conclude, moreover, that this evidence was sufficient for the jury also to infer that the defendant possessed an intent to kill, stemming from the permissible inference that the defendant had left the room to retrieve her gun and then returned to shoot the victim. “We have stated that [o]ne who uses a deadly weapon upon a vital part of another will be deemed to have intended the probable result of that act, and from such a circumstance a proper inference may be drawn in some cases that there was an intent to kill. . . . State v. Holley, 174 Conn. 22, 26, 381 A.2d 539 (1977).” (Internal quotation marks omitted.) State v. Stanley, 223 Conn. 674, 680, 613 A.2d 788 (1992).
Likewise, the jury was free to infer an intent to kill from the defendant’s failure to assist the victim after the shooting. We have previously noted that “the defendant’s failure to summon medical assistance for [her] victim [is] part of the evidence from which the jury could have inferred an intent to kill.” State v. Sivri, 231 Conn. 115, 129, 646 A.2d 169 (1994). Instead of seeking medical assistance for the victim, the defendant threatened Meyer not to tell anyone about the incident and immediately began the process of hiding the body. Consequently, there was sufficient evidence to support the jury’s finding that the defendant, when she shot the victim, had the requisite intent to kill him.
II
The defendant next claims that the trial court improperly denied her request to charge the jury on criminally negligent homicide as a lesser included offense of murder. In addition to charging murder, the trial court gave jury instructions on manslaughter in the first degree in violation of General Statutes § 53a-55 (a) (3)5 and [260]*260manslaughter in the second degree in violation of General Statutes § 53a-56 (a) (l).6 The trial court, however, concluded that the defendant was not entitled to a jury instruction on criminally negligent homicide because there was no evidence justifying conviction of the lesser offense. The state argues that the defendant failed to request an appropriate instruction.7 We agree with the state.
“There is no fundamental constitutional right to a jury instruction on every lesser included offense”; State v. Whistnant, 179 Conn. 576, 583, 427 A.2d 414 (1980); rather, the right to such an instruction is purely a matter of our common law. “A defendant is entitled to an instruction on a lesser [included] offense if, and only if, the following conditions are met: (1) an appropriate instruction is requested by either the state or the defendant; (2) it is not possible to commit the greater offense, in the manner described in the information or bill of particulars, without having first committed the lesser; (3) there is some evidence, introduced by either the state or the defendant, or by a combination of their proofs, which justifies conviction of the lesser offense; and (4) the proof on the element or elements which differentiate the lesser offense from the offense charged is sufficiently in dispute to permit the jury consistently to find the defendant innocent of the greater offense but guilty of the lesser.” Id., 588.
“In considering whether the defendant has satisfied the requirements set forth in State v. Whistnant, supra, [261]*261179 Conn. 588, we view the evidence in the light most favorable to the defendant’s request for a charge on the lesser included offense. State v. Montanez, 219 Conn. 16, 22-23, 592 A.2d 149 (1991); State v. Herring, 210 Conn. 78, 106, 554 A.2d 686, cert. denied, 492 U.S. 912, 109 S. Ct. 3230, 106 L. Ed. 2d 579 (1989). ‘[T]he jury’s role as fact-finder is so central to our jurisprudence that, in close cases, the trial court should generally opt in favor of giving an instruction on a lesser included offense, if it is requested. . . . Otherwise the defendant would lose the right to have the jury pass upon every factual issue fairly presented by the evidence.’ . . . State v. Rasmussen, 225 Conn. 55, 68, 621 A.2d 728 (1993). On appeal, an appellate court must reverse a trial court’s failure to give the requested instruction if ‘we cannot as a matter of law exclude [the] possibility’ that the defendant is guilty only of the lesser offense. State v. Falby, 187 Conn. 6, 30, 444 A.2d 213 (1982).” State v. Arena, 235 Conn. 67, 73-74, 663 A.2d 972 (1995).
Under the first prong of State v. Whistnant, supra, 179 Conn. 588, we must determine whether the request to charge constituted an appropriate instruction. “A proposed instruction on a lesser included offense constitutes an appropriate instruction for purposes of the first prong of Whistnant if it complies with Practice Book § 854. State v. Hall, 213 Conn. 579, 591, 569 A.2d 534 (1990); State v. Ostroski, [201 Conn. 534, 556-58, 518 A.2d 915 (1986)]; State v. McIntosh, [199 Conn. 155, 158-61, 506 A.2d 104 (1986)]. Section 854 provides in relevant part: ‘When there are several requests, they shall be in separate and numbered paragraphs, each containing a single proposition of law clearly and concisely stated with the citation of authority upon which it is based, and the evidence to which the proposition would apply . . . .’ ” (Emphasis added.) State v. Arena, supra, 235 Conn. 75. “We have held that, in the context of a written request to charge on a lesser [262]*262included offense, this requirement of § 854 is met only if the proposed request contains such a complete statement of the essential facts as would have justified the court in charging in the form requested.” (Internal quotation marks omitted.) State v. Hall, 213 Conn. 579, 591, 569 A.2d 534 (1990).
“ ‘While this court does not favor unyielding adherence to rules of procedure where the interests of justice are thereby disserved . . . the ever increasing refinement of our lawjustifi.es cooperation of counsel in stating requests for jury instruction. The minor burden of cooperation imposed by [Practice Book § 854] is neither unreasonable nor novel.’ . . . State v. Hall, supra, 213 Conn. 593.” State v. Arena, supra, 235 Conn. 75-76.
General Statutes § 53a-58 provides in pertinent part: “A person is guilty of criminally negligent homicide when, with criminal negligence, he causes the death of another person.” (Emphasis added.) “A person acts with ‘criminal negligence’ with respect to a result or to a circumstance described by a statute defining an offense when he fails to perceive a substantial and unjustifiable risk that such result will occur or that such circumstance exists.” General Statutes § 53a-3 (14). Accordingly, to comply with the first prong of State v. Whistnant, supra, 179 Conn. 588, and Practice Book § 854, the defendant’s request to charge must enumerate the essential facts to justify the court’s instruction to the jury pertaining to the defendant’s failure to “perceive a substantial and unjustifiable risk” of the victim’s death.
We conclude that the defendant’s request to charge did not set forth the essential facts to warrant the court’s instruction on criminally negligent homicide. The defendant’s request included the following facts: “You heard testimony that the victim was shot. However, the State’s witness Suzette Meyer testified that she did not actually see the defendant pull the trigger. She testified [263]*263that she was seated with her head down when the shot was fired. Suzette Meyer did not testify as to what caused the gun to be fired.” The request does not enumerate any essential facts demonstrating the defendant’s failure to “perceive a substantial and unjustifiable risk” of the victim’s death. We find unpersuasive the fact that Meyer did not actually see the defendant pull the trigger because that circumstance “is as applicable to the offenses of murder, manslaughter in the first degree, and manslaughter in the second degree as to criminally negligent homicide.”8 State v. Hall, supra, 213 Conn. 592. In our view, the defendant’s written request to charge constitutes “[a] mere general statement of the entire incident at issue [which] does not comply with our rules of practice.” Id., 591-92. Accordingly, the trial court did not improperly refuse the defendant’s request to instruct the jury on the offense of criminally negligent homicide.
Ill
The defendant’s final claim is that the trial court improperly admitted into evidence two tape-recorded conversations between the defendant and Meyer. We disagree.
The following additional facts are relevant to this issue. In September, 1992, after reading a newspaper article about the unsolved death of the victim, Meyer approached the local police and gave a statement implicating the defendant. In exchange for immunity, Meyer [264]*264agreed with the state’s attorney’s office to wear a recording device and to attempt to elicit an admission of guilt from the defendant.
On September 11,1992, Meyer and the defendant met at a local supermarket. The police had informed Meyer that the defendant would be at the supermarket at the designated time. Meyer, who was wearing a microphone in her baseball hat, met with the defendant and attempted to obtain an admission.9
[265]*265On September 15, 1992, the police tape-recorded a telephone conversation between Meyer and the defendant. Meyer telephoned the defendant from a police car, accompanied by police officers, and asked the defendant to call her back at a pay telephone. The telephone number that Meyer gave the defendant was actually that of the telephone she was then using in the police car. When the defendant returned Meyer’s telephone call, Meyer again attempted to elicit an admission.10
[266]*266At trial, the state offered the cassette tapes and transcripts of the conversations into evidence. The defendant objected, arguing that because Meyer was acting as an agent of the state, Miranda warnings were required. The trial court overruled the defendant’s objection, determining that there had been no custodial interrogation.11
The defendant argues that: (1) both recordings were improperly admitted because they were the product [267]*267of custodial interrogation and, consequently, Miranda warnings had been required; and (2) the recorded telephone conversation was improperly admitted because it constituted an intercepted wire communication in violation of General Statutes § 54-41/,.12 We disagree with each of these claims.
A
The defendant argues that, because the tape-recorded conversations occurred in a “police dominated environment,” Miranda warnings were required. We disagree.
“Two threshold conditions must be satisfied in order to invoke the warnings constitutionally required by Miranda: (1) the defendant must have been in custody; and (2) the defendant must have been subjected to police inteirogation. Miranda v. Arizona, [384 U.S. 436, 444, 86 S. Ct. 1602, 16 L. Ed. 2d 694 (1966)]. . . . State v. Williams, 227 Conn. 101, 112, 629 A.2d 402 (1993); accord State v. DesLaurier, 230 Conn. 572, 576, 646 A.2d 108 (1994). As stated by the United States Supreme Court in California v. Beheler, [463 U.S. 1121, 1125, 103 S. Ct. 3517, 77 L. Ed. 2d 1275 (1983)], [although the circumstances of each case must certainly influence a determination of whether a suspect is ‘in custody’ for [268]*268purposes of receiving Miranda protection, the ultimate inquiry is simply whether there is a formal arrest or restraint on freedom of movement of the degree associated with a formal arrest. [Oregon v. Mathiason, 429 U.S. 492, 495, 97 S. Ct. 711, 50 L. Ed. 2d 711 (1977)]. See also New York v. Quarles, 467 U.S. 649, 655, 104 S. Ct. 2626, 81 L. Ed. 2d 550 (1984); Minnesota v. Murphy, 465 U.S. 420, 430-31, 104 S. Ct. 1136, 79 L. Ed. 2d 409 (1984); United States v. Cadmus, 614 F. Sup. 367, 370 (S.D.N.Y. 1985). State v. Pittman, 209 Conn. 596, 608, 553 A.2d 155 (1989); accord State v. Ross, 230 Conn. 183, 204, 646 A.2d 1318 (1994), cert. denied, 513 U.S. 1165, 115 S. Ct. 1133, 130 L. Ed. 2d 1095 (1995); see also Thompson v. Keohane, [516 U.S. 99, 112, 116 S. Ct. 457, 133 L. Ed. 2d 383 (1995)]. Further, the United States Supreme Court has adopted an objective, reasonable person test for determining whether a defendant is in custody. . . . Thus, in determining whether Miranda rights are required, the only relevant inquiry is whether a reasonable person in the defendant’s position would believe that he or she was in police custody of the degree associated with a formal arrest. . . . State v. DesLaurier, supra, 577.
“Furthermore, we note that [n]o definitive list of factors governs a determination of whether a reasonable person in the defendant’s position would have believed that he or she was in custody. Because, however, the Miranda court expressed concern with protecting defendants against interrogations that take place in a ‘police-dominated atmosphere’ containing inherently compelling pressures which work to undermine the individual’s will to resist and to compel him to speak where he would not otherwise do so freely; Miranda v. Arizona, supra, 384 U.S. [467]; circumstances relating to those kinds of concerns are highly relevant on the custody issue. See generally C. Whitebread & C. Slobogin, Criminal Procedure (3d Ed. 1993) § 16.03, pp. [269]*269385-91; 1 W. LaFave & J. Israel, Criminal Procedure (1984) § 6.6, pp. 494-99. State v. DesLaurier, supra, 230 Conn. 577-78.
“The defendant bears the burden of proving custodial interrogation. State v. Pittman, supra, 209 Conn. 606. The trial court’s determination of the historical circumstances surrounding the defendant’s interrogation are findings of fact; id.; which will not be overturned unless they are clearly erroneous. State v. Young, 191 Conn. 636, 652, 469 A.2d 1189 (1983); State v. Ostroski, 186 Conn. 287, 292, 440 A.2d 984, cert. denied, 459 U.S. 878, 103 S. Ct. 173, 74 L. Ed. 2d 142 (1982); see Practice Book § 4061. In order to determine the ultimate issue of custody, however, we will conduct a scrupulous examination of the record; State v. Weidenhof, 205 Conn. 262, 267-68, 533 A.2d 545 (1987); in order to ascertain whether, in light of the totality of circumstances, the trial court’s finding is supported by substantial evidence. State v. Pittman, supra, 606; State v. Toste, 198 Conn. 573, 580, 504 A.2d 1036 (1986); State v. Alexander, 197 Conn. 180, 185, 496 A.2d 486 (1985).” (Emphasis in original; internal quotation marks omitted.) State v. Atkinson, 235 Conn. 748, 757-59, 670 A.2d 276 (1996).
Applying these principles to the facts of this case, we conclude that there is substantial evidence in the record to support the trial court’s conclusion that the defendant failed to prove that she was in custody during the course of either the September 11, 1992 meeting or the September 15, 1992 telephone conversation. At all times during the meeting in the supermarket, the defendant was free to leave. Meyer neither used, nor threatened to use, force to detain the defendant. Further', during the September 15,1992 telephone conversation, the defendant was not obligated to return Meyer’s telephone call. Indeed, the defendant could have terminated the conversation at any time by simply hanging [270]*270up the receiver. Accordingly, because a review of the facts in the record reveals that a reasonable person in the defendant’s position would not have believed that she was in custody, during either the supermarket meeting or the telephone conversation, we agree with the trial court’s conclusion that the defendant was not entitled to Miranda warnings.
B
The defendant next claims that the trial court improperly admitted into evidence the tape-recorded September 15,1992 telephone conversation in violation of § 54-41Í.13 See footnote 12. In particular, the defendant argues that, because she was not served with a copy of the court order authorizing the intercepted wire communication, a new trial is warranted.14 We disagree.
“In general terms, our wiretap act [General Statutes § 54-41a et seq.] provides that, based upon certain specified findings, a panel of three Superior Court judges may issue an order authorizing ‘the interception of wire communications within the state of Connecticut. . . .’ [271]*271General Statutes § 54-41d. For these purposes, ‘ “¡intercept” means the intentional overhearing or recording of a wire communication through the use of any electronic, mechanical or other device.’ General Statutes § 54-41a (Z).”15 State v. McVeigh, 224 Conn. 593, 604-605, [272]*272620 A.2d 133 (1993). Section 54-41l prohibits the contents of intercepted wire communications from being admitted into evidence unless the “aggrieved person” has been served with a copy of the court order at least thirty days before trial.
We have held, however, that the protections of the wiretap act are inapplicable to wiretaps in which one party consents to the recording. State v. Grullon, 212 Conn. 195, 211, 562 A.2d 481 (1989). In Grullon, we emphasized that “ ‘[t]he competing interests of the community in effective law enforcement and of the individual in his privacy are, in a unique way, drawn into question by police wiretapping. Clearly, our statutes are aimed at balancing these competing interests.’ ” Id., 210-11, quoting State v. Ross, 194 Conn. 447, 458, 481 A.2d 730 (1984). Accordingly, if one of the parties to a telephone conversation consents to wiretapping, the provisions of the wiretap act, including § 54-417, do not apply.
In this case, it is undisputed that Meyer consented to the wiretapping of the September 15, 1992 telephone conversation with the defendant. We conclude that, [273]*273because the wiretap act does not apply to consensual wiretaps, the state was under no statutory obligation to obtain a court order authorizing the wiretap or to give the defendant a copy of that order and the accompanying application.
The judgment is affirmed.
In this opinion PETERS, C. J., and NORCOTT and PALMER, Js., concurred.
BERDON, J. I concur in the result.