Can を used with だ/です? 君沢さんを犯人だと思い込む


I came across the following passage in a mystery manga. The main character is
explaining that the as of yet unknown criminal intentionally made the listener
think that Kimisawa was the criminal (though she is not).

> おそらく奴は **お前が君沢さんを犯人だと思い込む** のを計算に入れて、その「香水」の匂いをかがせたんだ！  
>  It's likely that that guy (奴) incorporated it into his plans that you'd be
> under the impression that the criminal was Kimisawa. He made you smell that
> perfume on purpose!

Unless I am mistaken, it seems to me that the subject/complement of だ is
denoted with を which I thought was unacceptable. Could someone please explain
when and if this is allowable?




`AをBだ` in isolation makes little sense (although there are minor
[exceptions](https://japanese.stackexchange.com/q/36207/5010)). This `～を～だと`
is a common pattern which appears along with various verbs for assuming,
regarding, etc.

  * AをBだと見なす to regard A as B
  * AをBだと考える to consider A B
  * AをBだと仮定する to assume A is B
  * AをBだとする to suppose A as B
  * AをBだと思う to think of A as B
  * AをBだと勘違いする to mistake A as B
  * AをBだと思い込む to make a wrong assumption that A is B
  * AをBだと定義する to define A as B
  * AをBだと受け取る to take A as B
  * AをBだと解釈する to interpret A as B

So `Bだと` is like `as B`, and these verbs can take both を and だと at the same
time.

**EDIT:** だ before を can be omitted in many cases. 君沢さんを犯人と思い込む (without だ)
and 君沢さんが犯人 **だ** と思い込む are equally correct. For details, see [Difference
between だと vs と before 認める](https://japanese.stackexchange.com/q/55990/5010)
and [grammatical and semantic difference of "嘘と思う" and
"嘘だと思う"](https://japanese.stackexchange.com/q/56540/5010)




`AをBだ` in isolation makes little sense (although there are minor
[exceptions](https://japanese.stackexchange.com/q/36207/5010)). This `～を～だと`
is a common pattern which appears along with various verbs for assuming,
regarding, etc.

  * AをBだと見なす to regard A as B
  * AをBだと考える to consider A B
  * AをBだと仮定する to assume A is B
  * AをBだとする to suppose A as B
  * AをBだと思う to think of A as B
  * AをBだと勘違いする to mistake A as B
  * AをBだと思い込む to make a wrong assumption that A is B
  * AをBだと定義する to define A as B
  * AをBだと受け取る to take A as B
  * AをBだと解釈する to interpret A as B

So `Bだと` is like `as B`, and these verbs can take both を and だと at the same
time.

**EDIT:** だ before を can be omitted in many cases. 君沢さんを犯人と思い込む (without だ)
and 君沢さんが犯人 **だ** と思い込む are equally correct. For details, see [Difference
between だと vs と before 認める](https://japanese.stackexchange.com/q/55990/5010)
and [grammatical and semantic difference of "嘘と思う" and
"嘘だと思う"](https://japanese.stackexchange.com/q/56540/5010)

