The threshold question presented by this appeal is whether the trial judge properly considered grounds for the suppression motion which were not contained in the motion itself.
General Statute 15A-977(a) dictates that all motions to suppress evidence must contain the grounds which defendant asserts as the basis of the motion. The motion presented by defendant in this case focused on the involuntary nature of defendant’s statements. The trial judge, on the other hand, based his decision granting the motion on the failure of the police to give the warnings required by Miranda for custodial interrogations.
[1] General Statute 15A-977(c) states “The judge may summarily deny the motion to suppress evidence if: (1) the motion does not allege a legal basis for the motion . . .” (Emphasis added.) Thus, the decision to deny summarily a motion which fails to set forth adequate legal grounds is vested in the sound discretion of the trial court. See State v. Smith, 50 N.C. App. 188, 272 S.E. 2d 621 (1980). The alternative is to hold a hearing on the motion, despite the facial insufficiency of the motion itself. Once the discretionary decision is made not to deny the motion summarily, a hearing must be held, G.S. 15A-977(d), and “the burden is on the state to demonstrate the admissibility of the challenged evidence; and in the case of a confession, the state must affirmatively show (1) the confession was voluntarily made, (2) the defendant was fully informed of his rights and (3) the defendant voluntarily waived his rights.” State v. Cheek, 307 N.C. 552, 557, 299 S.E. 2d 633, 636 (1983). The judge’s decision in this case was merely one that the State did not meet its burden of persuasion on the second point above — that the defendant was fully informed of his rights.
[2] A person must be fully informed of his rights whenever he is “in custody” of the police and before any interrogation of that person begins. Miranda, supra. The State contends that defendant here was not “in custody” within the meaning of Miranda when he was questioned by the officers, relying on California v. Beheler, 463 U.S. 1121, 103 S.Ct. 3517, 77 L.Ed. 2d 1275 (1983) and Beckwith v. United States, 425 U.S. 341, 96 S.Ct. 1612, 48 L.Ed. 2d 1 (1976). Those cases, however, present key factual differences from the case at hand. In Beckwith, the defendant was an educated, experienced businessman who was interviewed in a *238“relaxed” atmosphere in his home by two IRS agents who had informed him of his rights not to answer questions and to the presence of an attorney. Beckwith at 343, 96 S.Ct. at 1614-15, 48 L.Ed. 2d at 5. Here, the defendant is a 17-year-old boy with a tested IQ of 78 who was questioned by two officers far from home in a closed office, isolated in a police station. He was not advised of any of his constitutional rights until after he had made incriminating statements. In Beheler, the defendant was a participant in a robbery which resulted in the murder of the victim. Defendant Beheler, not wanting to be an accessory to murder, immediately phoned the police to report the crime and cooperated with the police fully throughout their investigation. Beheler at 1125, 103 S.Ct. at 3520, 77 L.Ed. 2d at 1280. In this case the police, not the defendant, initiated contact and defendant denied all involvement in the crimes for at least one hour of interrogation.
Custodial interrogation, requiring the Miranda warnings, is “questioning initiated by law enforcement officers after the person has been taken into custody or otherwise deprived of his freedom of action in any significant way.” Miranda at 444, 86 S.Ct. at 1612, 16 L.Ed. 2d at 706. The State contends that defendant was not in custody because the officers never planned to arrest him that day and, in fact, returned him home after he signed the confession prepared by the officers. However, “[a] policeman’s unarticulated plan has no bearing on the question whether a suspect was ‘in custody’ at a particular time; the only relevant inquiry is how a reasonable man in the suspect’s position would have understood his situation.” Berkemer v. McCarty, --- U.S. ---, ---, 104 S.Ct. 3138, 3152, 82 L.Ed. 2d 317, 336 (1984). Defendant here was taken far from his home, placed in a closed office with two officers, subjected to lengthy questioning and was never expressly told that he was not under arrest or that he was free to leave and could end the questioning at anytime. These factors, added to the defendant’s age and mental capacity, demonstrate the coercive nature of the interrogation and indicate that the Miranda warnings should have been given prior to any interrogation of defendant.
[3] Because the warnings were required prior to any questioning of defendant at the station, the incriminating oral statements made by defendant are inadmissible. By the same reasoning, the *239written statement was also properly excluded. The giving of the Miranda warnings prior to asking defendant to sign the prepared statement did not “cure” the coercive atmosphere, nor does it mean that by signing the statement defendant knowingly and intelligently waived his rights. See, e.g., Miranda at 479, 86 S.Ct. at 1630, 16 L.Ed. 2d at 726; Davis v. North Carolina, 384 U.S. 737, 86 S.Ct. 1761, 16 L.Ed. 2d 895 (1966).
[4] The State’s final assignment of error is that the findings of fact found by the trial judge are not supported by competent evidence. Specifically, the State asserts that the judge erred in basing his decision on an evaluation of the demeanor and credibility of one of the interrogating detectives, who was the only witness to testify at the suppression hearing. This contention is totally without merit. The principle is well-settled that evaluating the credibility and demeanor of a witness is a matter peculiarly reserved to the trier of fact. E.g., Brinkley v. Nationwide Mutual Insurance Co., 271 N.C. 301, 156 S.E. 2d 225 (1967). Because the State bears the burden of proving defendant was aware of his rights and knowingly, intelligently and voluntarily waived them, Cheek, supra, the trial court could properly rule against the State based on a negative finding as to the credibility and demeanor of the State’s only witness.
We find no error in the decision of the trial judge to grant defendant’s motion to suppress his oral and written statements given to the police on 13 June 1984, and the decision is hereby
Affirmed.
Judges Johnson and Eagles concur.