Difference between “testified” and “stated” in a legal context

Question

If you're working in a law firm, do the words "testified" and "stated" have two different meanings?

For example,

The witness testified that...
The witness stated that...

And is it acceptable to use the two as synonyms?

Answer 1

Black's Law Dictionary online states:

What is STATE, v? To express the particulars of a thing in writing or in words; to set down or set forth in detail. To set down in gross; to mention in general terms, or by way of reference; to refer. Utica v. Richardson, 6 Hill (N. Y.) 300. Read more: What is STATE, v? definition of STATE, v (Black's Law Dictionary)

It also states:

What is TESTIFY? To bear witness; to give evidence as a witness; to make a solemn declaration, under oath or affirmation, in a judicial inquiry, for the purpose of establishing or proving some fact. See State v. Robertson, 26 S. C. 117, 1 S. E. 443; Gannon v. Stevens, 13 Kan. 459; Nash v. Hoxie, 59 Wis. 384, 18 N. W. 408; O’Brien v. State, 125 Ind. 38, 25 N. E 137, 9 L. R. A. 323; Mudge v. Gilbert 43 How. Prac. (N. Y.) 221. Testimonia ponderanda sunt, non numeranda. Evidence is to be weighed, not enumerated. Read more: What is TESTIFY? definition of TESTIFY (Black's Law Dictionary)

There are lots of specialized dictionaries on the Net. It's a good idea to do research before asking a question that you can answer yourself.

Answer 2

You testify under oath. Part of the testimony is what you state. You can also state things outside of the legal proceedings.