-(으)ㄹ지도 모르다 — might happen

This expression is used to indicate the speaker's view that something might happen or could possibly. The form -(으)ㄹ지 모르다 is also used.

Details

1. Because this expression indicates something that is possible, but unlikely, to happen, it can come across as rude to a person who is worried about an event that is important to him or her.

가: 이번 시험에 꼭 합격해야 할 텐데요.

I've really got to pass this exam.

나: 열심히 공부했으니까 합격할지도 몰라요.

You've studied really hard, so maybe you'll pass.

가: 뭐라고요? 제가 떨어질 가능성이 더 많다는 얘기예요?

What? Are you saying it's more likely that I'll fail?

The phrase 합격할지도 몰라요 means that the speaker thinks the hearer might pass even though the chances of doing so are slim. Naturally, the hearer would feel bad upon hearing such a statement. In this case, therefore, it is better to use the phrase 합격할 거예요，which expresses the speaker's belief that there is a very high probability that the hearer will pass.

2. The past tense form of this expression is -았/었을지도 몰라요. It is incorrect to change 몰라요 to 몰랐어요,

게이코 씨가 파티에 간다고 했지만 안 갔을지도 몰랐어요. ✕

Kimchi Reader

Used to indicate that something might happen or could possibly occur.