(ちが)いない

ちがいない
expression
no doubt, must be, certain
1. no doubt, must be, certainly
Expresses strong certainty or conviction that something is true.
He must know about it.
(ちが)いない pattern
これ本物(ほんもの)(ちが)いない。
This must be genuine.
The culprit must be him.
Judging from her behavior, she must be hiding something.
The fact that the road is this congested means there must have been an accident up ahead.

GRAMMAR PATTERN:
(ちが)いない = must be ~, no doubt ~

Used after:

SIMILAR EXPRESSIONS (certainty levels):

NOTE:
(ちが)いない expresses the speaker's strong conviction, often based on evidence or reasoning.