Dead Giveaway 

An incontrovertible sign that something is the case, that it is true.

"There were many things that pointed to murder, but the dead giveaway was when they found the bloody knife buried in a freshly dug hole in the backyard."

"Her failure to disclose her relation with the victim was a dead giveaway that something was very wrong with her testimony."

Dead Giveaway by ScorpionWasp December 10, 2015

Dead Giveaway 

When all of the facts, and or implications of an event are brought to light, sometimes related to rescuing victims.

Example 1:“I knew something was wrong when a little pretty white girl ran into my black neighbor’s arms. Dead giveaway. Dead giveaway.”

Dead Giveaway by juoni May 9, 2013

Dead Giveaway 

1. Something that's proof/logical without proving it. It can also be expressed as "a dead giveaway."

2. A obvious giveaway or a sign.

3. Understanding that reveals itself.

What you say and what you do, together, are dead giveaways.

Dead Giveaway by Mr. Terrence L. Trezvant April 9, 2006