家庭内の殺人が多いのは、密室で目撃者もなく殺しやすいからって英語でなんて言うの？

ご質問ありがとうございます。

少し長い文章になってしまいましたが...

"The reason why many murders take place inside the home is"=「家庭内の殺人が多い理由は」

"because they take place behind closed doors,"＝「密室で行われるから」

"which makes it easy for people to commit murder."＝「それは殺人を実行しやすくするから。」

ご参考に。

"家庭内の殺人が多いのは、密室で目撃者もなく殺しやすいから"
- The reason why there are so many domestic murders is because it is easy to kill behind closed doors without any witnesses.

• There are many murders that take place inside a home since its a private area and because there aren’t any witnesses.