GRAMMAR DETAIL

ことだから

knowing ..., one can expect ...

Infers a familiar person's likely behavior from their known character or usual conduct.

Examples

彼のことだから、予定に間に合わなくても必ず連絡してくるだろう。

Knowing him, he will certainly contact us even if he cannot make it on time.

彼女のことだから、きっと約束を守るだろう。

Knowing her, she will surely keep her promise.

慎重な彼のことだから、事前に十分調べているだろう。

Knowing how cautious he is, he has probably researched it thoroughly in advance.

Structure: のことだから follows a person to predict their behavior from their familiar character or usual conduct.
Basic usage: 慎重な彼のことだから、事前に十分調べているだろう。 infers from his cautious nature that he has probably researched the matter beforehand.

Using a familiar disposition as grounds
- 彼のことだから約束を守るだろう makes a prediction based on knowing him. 約束したから守るだろう bases it on the particular act of making a promise, distinguishing knowledge of a person from an individual event.
The time of the inferred action
- 調べているだろう can infer that the research is already done, while 調べるだろう can predict research yet to come. The following verb form specifies the time of the behavior inferred with のことだから.