Must Have Done: The Detective Tense
Modal + have + V3 is the detective's toolkit: must have done (almost sure), might have done (possible), can't have done (impossible), should have done (regret).
Modal + Have + V3
Deductions about the past
This structure is the detective’s toolkit: it reads the evidence of the past and makes a guess about what must have happened. The modal sets the certainty; have + V3 carries the past.
Must have + V3 — almost sure
the evidence is strongShe must have left early
Might / may have + V3 — possible
one guess among manyHe might have missed the bus
Can't have + V3 — impossible
the evidence says noThey can't have finished already
Should have + V3 — regret
the right thing was not doneI should have called you
⚠️ A deduction about the past: modal + have + V3.
The Formula
modal + have + past participle
One machine, four moods: the modal chooses the certainty, have connects to the past, and the V3 participle carries the action. The verb after have is always the participle.
Shemust have leftearly
Hemight have missedthe bus
Theycan't have finishedalready
Ishould have calledyou
Common Mistakes
Four detective slips
The deduction collapses when have is replaced by has, when have disappears entirely, or when the participle forgets its shape.
She must has left early.
She must have left early.
💡 After the modal comes have — never has.
He must left early.
He must have left early.
💡 The V3 needs have in front.
I should have call you.
I should have called you.
💡 have + V3: call → called.
He can't has done it.
He can't have done it.
💡 can't + have + V3 — have never changes.
Quick Quiz
Test what you just learned
Three minutes, five questions — check what stuck. No essay questions, we promise.
The lights are off — she ___ have gone to bed.
💡 Info tambahan2 bagian
The Deduction Scale
From impossible to almost sure
Every deduction sits somewhere on this scale. The evidence decides where.
The Detective’s Kit
Five tools, five jobs
The detective carries five tools. Match each one with its job.
⚠️ Could have done is the saddest tool: the chance existed, but it was missed.