The issue on appeal is whether the Court of Appeals incorrectly refused to enforce I.C.R. 12(d), a rule of procedural default, by requiring the trial court to render findings of fact as to the voluntariness of the defendant’s confession where findings were not requested by either of the parties.
Miles “Mike” Kirkwood was convicted by a jury of first-degree murder for stabbing his ex-wife to death in her home. Police arrested Kirkwood at the house and took him to the Ada County jail, where he gave two statements admitting the killing. The record contained conflicting evidence regarding whether the first confession was involuntarily induced by coercive treatment by the police. Accordingly, Kirkwood asserted that the second confession was “fruit of the poisonous tree” and, thus, also inadmissible. Kirkwood was read his Miranda rights prior to both statements and signed documents acknowledging that he had been given those rights and that he understood them.
Prior to trial, Kirkwood moved to suppress the confessions. The trial judge took the motion under advisement and instructed both parties that he would inform them of his decision prior to trial. It appears from the record that the trial judge inadvertently failed to rule on the motion, and proceeded as if the motion had been denied, admitting the confessions.1 During the trial, defense counsel did not object to the admission of the taped confessions, and the trial proceeded twelve days after the suppression hearing without the court having ruled on the motion. Subsequently, Kirk-wood was convicted by a jury of first-degree murder.
On appeal, the Court of Appeals ruled that the trial court’s failure to make factual findings as to whether the confessions were voluntary, necessitated that Kirk-wood’s conviction be vacated and the case remanded to the trial court for findings of fact.
The Court of Appeals, in ruling that such findings of fact constituted an exception to the I.C.R. 12(d) requirement providing that the trial court make factual findings only “upon the request of any party,” held that an appellate court could not resolve the *625ultimate question of voluntariness without some “basic facts.” The Court of Appeals, in vacating the judgment of conviction and remanding, 110 Idaho 97, 714 P.2d 66, directed the trial court to make findings of fact as to whether the confessions were voluntary.
We set aside the decision of the Court of Appeals and affirm the judgment of conviction.
I.C.R. 12(d) provides:
Ruling on motion. — A motion made before trial shall be determined before trial unless the court orders that it be deferred for determination at the trial of the general issue. When factual issues are involved in the determination of the motion, the court, upon the request of any party, shall make its findings thereon. (Emphasis added).
Rule 12(e) further provides:
Effect of failure to raise defenses or objections. — Failure by the defendant to raise defenses or objections or to make requests which must be made prior to trial, or at the time set by the court pursuant so subsection (c), or prior to any extension thereof made by the court, shall constitute waiver thereof, but the court for cause shown may grant relief from the waiver. (Emphasis added).
This Court has held that the question of voluntariness is controlled by State v. Dillon, 93 Idaho 698, 471 P.2d 553 (1970), cert. den.; Dillon v. Idaho, 401 U.S. 942, 91 S.Ct. 947, 28 L.Ed.2d 223 (1971), which established the rule that the question of the “voluntariness [of defendant’s statement] is, in the first instance, a question of law for the trial court.” State v. Mitchell, 104 Idaho 493, 495, 660 P.2d 1336, 1338, cert. den.; Mitchell v. Idaho, 461 U.S. 934, 103 S.Ct. 2101, 77 L.Ed.2d 308 (1983). In Dillon, supra, we adopted the so-called “Massachusetts rule” holding that:
“[t]he trial court in the absence of the jury resolves the issue of voluntariness and then determines the admissibility of a criminal defendant’s statements. The trial court must find them to have been shown to be admissible by a preponderance of the evidence.” Dillon, [93 Idaho] at 709-10, 471 P.2d at 564-65 (footnote omitted).
Although not conclusive, an express written statement waiving Miranda rights is usually strong proof of voluntary waiver. State v. Padilla, 101 Idaho 713, 719, 620 P.2d 286, 292 (1980). Additionally, “[I]n [a suppression hearing] the power to judge the credibility of the witnesses, resolve any conflicts in the testimony, weigh the evidence and draw factual inferences, is vested in the trial court.” People v. Lawler, 9 Cal.3d 156, 107 Cal.Rptr. 13, 15, 507 P.2d 621, 623 (1973). The implicit findings of the trial court, (i.e., that statements of the defendant made to the police were voluntary and should not be suppressed) should be overturned only if not supported by substantial evidence. See Mitchell, supra 104 Idaho at 500, 660 P.2d at 1341.
The Supreme Court of California has stated that on appeal of a motion to suppress evidence:
“[a]ll presumptions favor the [trial court’s] exercise of [the power to weight the evidence and draw factual inferences] and the trial court’s findings on such matters, whether express or implied, must be upheld if they are supported by substantial evidence.” Lawler, 507 P.2d at 623 (emphasis added).
Kirkwood claims that motions to suppress evidence are governed by the “fundamental error” doctrine, which, in effect, would preclude the defense attorney from ever waiving any objection. In State v. Kelly, 106 Idaho 268, 678 P.2d 60 (Ct.App. 1984) cert. den. and Kelly v. Idaho, 469 U.S. 918, 105 S.Ct. 296, 83 L.Ed.2d 231 (1984), the Court of Appeals addressed this argument, noting that:
“[suppression of evidence is a matter required by Rule 12, I.C.R., to be raised before trial. If an issue relating to suppression of evidence is not timely raised before trial, it is waived. A district *626court, as a matter of discretion, may— but is not required to — consider the issue later. [Citations omitted]. However, where — as here — the asserted error relates not to infringement upon a constitutional right, but to' violation of a rule or statute, we hold that the “fundamental error” doctrine is not invoked.” Id. 106 Idaho at 277, 678 P.2d at 69. (Emphasis added).
However, even “fundamental rights” may be waived. As the Supreme Court of Washington noted, the fact that the rights are of constitutional magnitude does not prevent a waiver. State v. Myers, 545 Wash.2d 538, 545 P.2d 538, 543 (1976). See, e.g., Rasmussen v. Tahash, 272 Minn. 539, 141 N.W.2d 3 (1965) (Defendant waived right to object to the introduction of confession by not requesting a hearing on the voluntariness of his confession); State v. McDaniel, 136 Ariz. 188, 665 P.2d 70 (1983) (the failure to object to offer of evidence is a waiver of any ground of complaint against its admission); State v. Miles, 233 Kan. 286, 662 P.2d 1227 (1983) (absent some objection or motion by defendant to the admission of his confession or admission, the United States Constitution does not require a hearing on voluntariness to be held prior to the confession’s admission into evidence).
In Myers, supra, the trial judge, despite a rule requiring the formal entry of written findings of fact, “did not make any findings on the question of whether the statements were voluntarily made, and no formal written findings were otherwise made. The appellant contended] that under these circumstances ... the case should be remanded for a determination of whether the statements in question were made voluntarily.” 545 P.2d at 543. The court noted that since no objection was made, the conduct of the appellant was sufficient to constitute an effective waiver. 545 P.2d at 543. In light of the authority cited, Kirkwood’s failure to object at trial to the admission of his confession was an effective waiver to a complaint that such confession was not voluntarily made.
Kirkwood next argues that Jackson v. Denno, 378 U.S. 368, 84 S.Ct. 1774, 12 L.Ed.2d 908 (1964) stands for the proposition that the accused must have a clear-cut and reliable determination of the voluntariness of his confession before it can be introduced against him at trial, apparently contending that a failure to render an explicit determination obviates his waiver. The U.S. Supreme Court, however, has addressed and rejected this argument. In Wainright v. Sykes, 433 U.S. 72, 97 S.Ct. 2497, 53 L.Ed.2d 594 reh. den., 434 U.S. 880, 98 S.Ct. 241, 54 L.Ed.2d 163 (1977), the defendant urged, as does Kirkwood, that Jackson v. Denno, supra, requires a voluntariness hearing despite defendant’s failure to object. In rejecting this argument, Justice Rehnquist, speaking for the majority noted that:
Respondent ... urges that a defendant has a right under Jackson v. Denno, 378 U.S. 368, 84 S.Ct. 1774, 12 L.Ed.2d 908 (1964), to a hearing as to the voluntariness of a confession, even though the defendant does not object to its admission. But we do not read Jackson as creating any such requirement. In that case the defendant’s objection to the use of his confession was brought to the attention of the trial court, ... and nothing in the Court’s opinion suggests that a hearing would have been required even if it had not been. To the contrary, the Court prefaced its entire discussion of the merits of the case with a statement of the constitutional rule that was to prove dispositive — that a defendant has a “right at some stage in the proceedings to object to the use of the confession and to have a fair hearing and a reliable determination on the issue of voluntariness____” “Language in subsequent decisions of this Court has reaffirmed the view that the Constitution does not require a voluntariness hearing absent some contemporaneous challenge to the use of the confession.” Wainright, su*627pra, at 86, 97 S.Ct. at 2506 (Citations and footnote omitted. Emphasis added.).
The Court went on to note that the “Florida procedure [requiring contemporaneous objection] did, consistently with the United States Constitution, require that respondents’confession be challenged at trial or not at all, and thus ... failure to timely object to its admission amounted to an independent and adequate state procedural ground which would have prevented direct review here.” Id. at 86-7, 97 S.Ct. at 2506.
The rationale of this rule may be justified when one realizes that the failure to make objection is often a matter of trial tactics—an effort by the defendants' counsel to “create error” at the trial court level. Generally, the failure to make objection is a matter of trial tactics as to which the court will not exercise judicial hindsight. People v. Lanphear, 28 Cal.3d 463, 171 Cal.Rptr. 505, 622 P.2d 950 (1980), appeal after remand, 36 Cal.3d 163, 203 Cal.Rptr. 122, 680 P.2d 1081 (1984) (disapproved on other grounds) in Wainwright v. Witt, 469 U.S. 412, 105 S.Ct. 844, 83 L.Ed.2d 841 (1985).
As this Court noted in Shaddy v. Daley, 58 Idaho 536, 76 P.2d 279 (1938), “[i]f, during the course of a trial, counsel for one of the parties’ litigant is guilty of conduct which counsel for the other party believes is prejudicial to his client’s rights, it is the duty of the latter to make objection thereto, and to ask that the jury be instructed to disregard it, or to move for an order declaring a mistrial. A litigant is not permitted to remain silent under such circumstances with a view of accepting the benefits of a judgment if he wins and of having it vacated and set aside if he loses [citations omitted].” 76 P.2d 279, 281 (emphasis added).
We hold, therefore, that I.C.R. 12(d), does not require the trial court to render explicit findings of fact as to the voluntariness of the defendant's confession, where none are requested by either of the parties, and, as here, admission of the confession at trial operated, ipso facto, as a ruling that the confession was voluntarily made.
Due to our holding today, and the implicit ruling of the District Court, i.e., that Kirkwood made a knowing, intelligent, and voluntary confession, we address the second issue briefed by counsel for the appellant summarily. Kirkwood’s first confession was found, implicitly, by the trial court to be voluntary. Accordingly, Kirkwood’s contention that his second confession was a direct product of his first allegedly illegally obtained confession, must fail.
Kirkwood next challenges the sufficiency of the evidence to support the jury finding the existence of a deliberate and premeditated killing beyond a reasonable doubt. In matters relating to the sufficiency of evidence, the scope of appellate review is limited. A judgment of conviction will not be set aside on appeal if there is substantial, competent evidence to support it. State v. Horn, 101 Idaho 192, 610 P.2d 551 (1980); State v. Holder, 100 Idaho 129, 594 P.2d 639 (1979). Where the evidence is not legally insufficient, the determination of premeditation rests entirely with the trier of fact. State v. Foley, 95 Idaho 222, 506 P.2d 119 (1973). “On appeal, where a defendant stands convicted, [the court will] view the evidence most favorably to the prosecution. [Citation omitted]. A mere possibility of innocence will not invalidate a verdict of guilty on appeal.” State v. Fenley, 103 Idaho 199, 204, 646 P.2d 441, 446 (Ct.App.1982).
Kirkwood’s own statements established substantial and competent evidence of premeditation. Upon his arrest, Kirk-wood told the arresting officer that he had entered his ex-wife’s home with a concealed knife. Before killing his ex-wife, Kirkwood told her that he was going to kill her. Kirkwood also testified that his ex-wife had not allowed him to see his children for two weeks, and that she had been cheating on him. Additional testimony indicated that Kirkwood had attempted to purchase a gun for the purpose of killing his ex-wife. Ac*628cordingly, the jury’s verdict is supported by substantial and competent evidence.
The decision of the Court of Appeals is set aside and the judgment of conviction is affirmed.
DONALDSON, C.J., and SHEPARD and BAKES, JJ., concur.. In the Court of Appeals at oral argument, counsel for the State presented a letter from the district court judge stating that the motion had been denied. However, defense counsel said he had no record of such a letter nor is such a letter part of the record before us.