expression, godan verb (-ku)
lack a decisive factor; lack conclusive evidence; lack a trump card
Used when a situation, argument, or plan is missing the crucial element that would settle it. Often appears in legal, investigative, or competitive contexts. The cross-reference 決め手に欠ける is a synonymous expression.
See also: 決め手に欠ける
この事件は決め手を欠いているため、捜査が難航している。
The investigation is stalled because this case lacks conclusive evidence.
His proposal isn't bad, but it was shelved because it lacks a decisive factor.