YOU SAID:
The police plan to investigate this
INTO JAPANESE
警察はこれを調査する計画
BACK INTO ENGLISH
The police plan to investigate this.
INTO JAPANESE
警察はこれを調査する予定です。
BACK INTO ENGLISH
The police are going to investigate this.
INTO JAPANESE
警察はこれを調査するつもりです。
BACK INTO ENGLISH
The police are going to investigate this.
That didn't even make that much sense in English.