I wouldn't say that, it implies guilt (by the letter of the law and justice an innocent person's life wouldn't depend on them keeping their mouth shut).
Further more, the specific phrase "my life might depend on me keeping my mouth shut" could be interpreted by a cop as being more than what you mean - eg maybe you are harboring a criminal who has threatened to kill you.
As geeks, I think we have a tendency to 'front load' a lot of this as we try to explain our logic. A short "No comment" is best and the more you say, even in trying to justify your logic, opens up opportunity for a cop to use something against you.