(dissenting). I respectfully dissent from the majority’s conclusion that a judge can properly ascertain — sight unseen — the prejudicial and probative character of demonstrative evidence. It is axiomatic that the judge’s obligation to provide a fair trial to a criminal defendant requires attentiveness to ensure that jury findings are based on proper evidence, properly admitted, and not on what our cases refer to as “inflamed emotions.” See Commonwealth v. Berry, 420 Mass. 95, 109 (1995) (“trial judges must take care to avoid exposing the jury unnecessarily to inflammatory material that might inflame the jurors’ emotions and possibly deprive the defendant of an impartial jury”).
The defendant objected repeatedly to the admission of the ninety-second video “clip” here at issue.1 The majority concludes that the defendant nevertheless failed to preserve the issue because he did not also complain during the trial about the manner in which the judge reached his decision. However, we require preservation of error so that the judge has an opportunity to correct potential error, and avoid unnecessary appeal. See Commonwealth v. McDuffee, 379 Mass. 353, 359 (1979). Here, the judge was fairly placed on notice that admission of the video clip was potential error because it might be significantly more prejudicial than probative.2 The standard of review is not properly invoked to overlook nonperformance by the judge simply because the judge, specifically alerted to the issue, chose to act on assumption rather than firsthand investigation. He was explicitly asked by the defendant to perform his role as a gatekeeper and did not do so. Cf. Commonwealth v. Bastarache, 382 Mass. 86, 106 (1980) (affirming admission of inflammatory and altered photographs, noting that in such cases “the judge should carefully assess” them).
I must also differ with my colleagues on the claimed salutary effect of the judge’s review of other materials, or his discussions with counsel about the graphic images and the video clip. In blunt terms, ninety seconds is a long time to watch a man *598strangle a naked woman to death. Second-hand descriptions do not replicate the effect — indeed they do not even tell us what the effect might be. Caricature or imitation may be seriously unsettling depending on the realism with which they portray an unsavory reality. The extent to which this evidence may have prejudiced the jury unfairly is therefore a question of nuance and impression. Alternatively, and far more serious, a so-called “snuff” movie — a filmed record of a real murder — is in an altogether different and far more powerful category when our task is to determine prejudicial effect. Descriptions by lawyers do not provide a substitute for the judge’s obligation to observe and experience. Words, albeit our stock in trade, are simply deficient here. The judge was duty bound to observe the proffered evidence, and decide.
The fact that the judge viewed still photographs and other evidence exacerbates the problem in my opinion, because it is the effect of all the admitted evidence that is at issue. An essential aspect of balancing probative value with prejudicial effect is considering cumulative effect; the judge cannot consider each piece of evidence as though the others did not exist. See Commonwealth v. Lawrence, 404 Mass. 378, 390 (1989) (judge properly excluded photographs “he found cumulative and possibly prejudicial”). See also Mass. G. Evid. § 403 (2011).
The Commonwealth points out that only a small portion of the total materials found on the defendant’s computer was admitted. The obvious corollary is that there was good reason for drastic editing. Materials of this nature must be carefully selected to ensure that prejudicial material, even assuming probative value, is not needlessly repetitive.3 Our viewing confirms that both the photographs and the clip are highly realistic and inflammatory by any conventional standard. In such a case there is a point at which the probative value of the additional inflammatory evidence is reduced or eliminated. The judge could not determine whether this was so, or where that point might be found, because he did not examine the video clip.
A judge has no discretion whether to exercise discretion; *599failure to do so is treated as a variant of abuse of discretion, hence error, by our cases. Commonwealth v. Fredette, 56 Mass. App. Ct. 253, 259 n.10 (2002). See Commonwealth v. Manning, 47 Mass. App. Ct. 923 (1999). I fully endorse the general applicability of the cases cited by the majority in its comprehensive decision, and especially those that speak to the trial judge’s broad discretion. None of them, however, addresses a failure to look at demonstrative evidence after the defendant has objected to its admission, suggesting that this instance is unusual.4
For the reasons set forth above I conclude the error was prejudicial. Simply stated, it deprived the defendant of the judge’s obligation to determine independently whether the passions of the jury would be inflamed to a degree that outweighed the probative value of evidence indicating only a propensity to commit the crime.
The convictions should be vacated and the case remanded for proceedings which include a proper basis for evidentiary rulings.
The judge noted on the record that the defendant had preserved the issue.
Even on this record it is clear that the probative value of the video clip was secondary; it had no relevance to the actual crime and went exclusively to state of mind.
Commonwealth v. Jaundoo, 64 Mass. App. Ct. 56, 63 (2005) (reversible error to admit “great quantity of [sexual] materials, much of which had no direct bearing on the complainant’s testimony”).
See, e.g., Commonwealth v. Petrillo, 50 Mass. App. Ct. 104, 107 (2000), cert. denied, 532 U.S. 1030 (2001) (harmless error in admission of portion of videotape after “the judge observed the videotapes”).