According to Justice Kennedy, the reason why the Court of Appeals overturned Alvarado’s conviction is:
This refers to a legal verdict whereby a person is found guilty of an offence in a competent court of law and given a sentence.
With this in mind, we can see that the case of Alvarado was not one that was very straightforward because of the feelings of being in custody and being coerced by police tactics and thus the verdict was overturned because the Court said that being "in custody" was a matter of law, not of whether Alvarado believed he was in custody.
Read more about convictions here:
https://brainly.com/question/25480701