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admitted if its probative value is outweighed by the risk of
unfair prejudice to the defendant. See Commonwealth v. Crayton,
470 Mass. 228, 249 (2014).
Evidence of Jaszek's bad temper and poor treatment of his
students was relevant for at least one nonpropensity purpose.
Specifically, the evidence explained why the victim did not
disclose the assault at the time, i.e., that she was scared of
Jaszek and did not want him to be mad at her. Testimony from
other witnesses about Jaszek's temper tended to corroborate the
victim's testimony and so was relevant to her credibility and
the accuracy of her memory, which were decisive issues here.
See Commonwealth v. Kindell, 84 Mass. App. Ct. 183, 188 (2013)
(witness's credibility is relevant issue in any case).
Thus, the evidence was admissible unless its prejudicial
effect outweighed its probative value. In general, this risk is
low in a jury-waived trial, because the judge is presumed to
have applied correct principles of law and not to have relied on
evidence for an improper purpose. See Commonwealth v. Milo M.,
433 Mass. 149, 152 (2001); Commonwealth v. Dragotta, 89 Mass.
App. Ct. 119, 128 (2016), S.C., 476 Mass. 680 (2017). Here, the
amount of evidence about Jaszek's temper appears to have been
excessive. But, even assuming that some of the testimony would
have been excluded had there been an objection, Jaszek has not
argued on appeal that the judge considered the evidence for an