"As" is a frequently used word in English and has many parts of speech including preposition, adverb and conjunction.
Here are two sentence which both have used the phrase "as...as":
1) You're as tall as your father.
2) I have as much confidence in you as in him.
It is apparent that the former "as" in both sentence is an adverb. But what's the part of speech of the latter? A preposition in sentence 1 and a conjunction in sentence 2? Does it mean the latter "as" in this phrase has no fixed function, and its part of speech depends on the context of the sentence?
And one more question: What is the part of speech of "as" in this sentence: We demonstrate that she is the murder as indicated by the knife with her blood.