expression, ichidan verb
lack a decisive factor; lack a trump card; lack conclusive evidence
Used when a situation, argument, or investigation is missing the one decisive element that would settle it. Often appears in contexts like debates, games, or criminal cases.
彼の主張はもっともだが、決め手に欠ける。
His argument is reasonable, but it lacks a decisive factor.
捜査は進んでいるが
The investigation is progressing, but it still lacks conclusive evidence.