For certain and Without a shadow of a doubt

For certain adverb - Definitely or positively (`sure' is sometimes used informally for `surely').

Without a shadow of a doubt and for certain are semantically related. In some cases you can use "Without a shadow of a doubt" instead an adverb phrase "For certain".

For certain and without a shadow of a doubt are semantically related. You can use "For certain" instead an adverb phrase "Without a shadow of a doubt".