I am actually six feet tall. But if I tell you that I am seven feet tall is that evidence that I am seven feet tall?
Yes. The claim is being made for the purpose of supporting a purported fact. That's what makes it evidence. Testimony is notorious for being weak evidence, but evidence it is still.
A testimony is nothing more than a testimony. Other factors determine whether a testimony can be accepted as evidence. A testimony alone is just someone describing something according to their experience. Or it may be a case of self deception, illusion, poor observational skill, etc, but the value of the testimony needs to be determined by further inquiry.
Many years ago, I watched an hilarious scene on America's Dumbest Criminals where a cop entered a small cafe and spotted a wanted suspect. The cop approached and questioned him about his whereabouts, etc. To defend himself, the suspect explained that someone had been spreading his fingerprints all over town. That was some funny stuff!
It's ludicrous, of course, but (But!), that was his explanation. That was his explanation (or reason given) to support the notion that he was innocent of the alleged crimes to which he's been accused. This is where we might want some evidence to support his explanation, but there's more going on here than meets the eye if we go off in pursuit of that evidence. Goalposts have been shifted. I'm going to divert to a simpler example, discuss another matter, and finally revisit this example.
Little Johnny, a middle school student, who sat near the back of class was asked by the teacher Ms. White if he played hooky yesterday. He said, "No Ms. White, I didn't play hooky." Then, the teacher asks him why he didn't come to class yesterday. He explained why (or gave reason for) not showing up to class: "I broke my arm", he says. The teacher upon hearing this explanation became somewhat suspicious because little Johnny had a big grin on his face, so Ms White asked if he could provide any evidence to support his claim. He proudly stood up thereby putting on full display for all the class to see the arm-cast that was recently put on his arm.
Let's start out with what we can call an original claim. That is not evidence. If that claim is brought into contention, I might be pressed to bring in support of that claim. Whatever I bring in, be it physical or verbally explanatory, so long as it's being used to support the original claim, it is evidence, good or bad. Even another claim, so long as it's not a rehash of the original claim, is evidence. Yes, you might want evidence to support even that secondary claim, but that doesn't alter it's status as being evidence for the original.
The statement that he didn't play hooky is an original claim. It had support, but at the time it was uttered, no support had been offered. The statement made later, "I broke my arm", though a claim in its own right, also had support not brought forward at that time, but while the original claim is not evidence, as it wasn't a claim used to support another, the later claim is in fact evidence. Yes, as far as Ms. White was concerned, that claim too warranted further investigation. She wanted evidence further collaborating not just that he didn't play hooky but that he in fact broke his arm. Instead of showing the cast, what if the kid brought his mother and Doctor in to collaborate his story? Maybe even a few fake X-rays to go along with that stolen cast to boot, lol.
The dumb criminal wanted the cop to believe he was innocent of the looming charges, and to support that notion, he explained himself, but because it was used to support (nevermind success or veracity) an original position, it qualifies (lousy as it might be) as evidence.
There are facts (worldly affairs), and there are statements about those facts, but statements too are facts; in fact, pun intended, "facts" is ambiguous and can mean either; thus, we can have facts about facts. A 911 caller said, "I shot my wife." At trial, he denied that he did. The tape was played. His saying it is evidence he did it, even if he didn't, and the 911 tape is evidence he said it, even if someone else did.
People have an intuitive notion that this is supposed to make sense, as if there must be a direct trace between evidence and what it's evidence of, but nope; it's as screwy as it sounds. The best we can do is play ping pong.