。
If you stay silent, it amounts to admitting guilt.
Literal
Be-silent-is [when-と] crime [object-を] acknowledged [thing-こと] [become-に-なる] [emphatic-よ].
~ことになる is one of the indispensable Japanese aspectual frames — 'it comes to be the case that X, it ends up being X.' Often used for outcomes that follow automatically or are decided by circumstances rather than the speaker's choice. Here it makes the silence-admitting-guilt link feel like an inevitable consequence rather than an active choice. The と at the start is the conditional/temporal marker.