is a notarized response to a civil discovery request for admissions sufficient for "under oath"

Arguably, yes. But you might want to wait for Vasilas to come out of the CCA (again--the second trip to Austin). In that case, the defense is claiming that the rules of civil procedure trump the penal code when it comes to false pleadings.

This is a response made by a pro se defendant in a civil lawsuit where a defendant on probation for agg sex assault of a child was sued by his victim(who is now legally an adult). It was a nasty case that was pled to probation because of interference by the victim's mother(among other reasons). Desperately would like to revoke him. He acknowledged lying on the discovery responses when he was in court under oath at the trial of the civil case.

The notary statement reads "This instrument was acknowledged before em on the......" Signed notary public.

Am I wasting my time trying to do anything with this?

An acknowledgement is nothing more than a verification that the person whose name is on the document actually signed the document. It is NOT an affidavit.

Answers to requests for admissions are admissible ONLY in the same suit. Tex.R.Civ.P. 198.3; Osteen v. Glynn Dodson, Inc., 875 S.W.2d 429, 431 (Tex.App. - Waco 1994, writ denied).

A party cannot introduce into evidence a party's denial or refusal to admit a fact. See Americana Motel v. Johnson, 610 S.W.2d 143, 143 (Tex. 1980). When a party denies or refuses to make an admission of fact, it is nothing more than a refusal to admit a fact; it is NOT evidence of any fact except the fact of refusal. Newman v. Utica Nat'l Ins. Co., 868 S.W.2d 5, 8 (Tex.App. - Houston [1st Dist.] 1993, writ denied).

It seems to me that you are trying to hang your hat on the fact that this guy made a denial to one of the requests for admissions in that lawsuit for something for which he was found guilty or plead guilty to in your criminal case.
These cases above show you why it makes no difference.

I would caution you on the fact that you run the very real risk of poisoning or ruining the civil case. If it appears that you are using the criminal justice system as a way of allowing this victim to gain an unfair advanatge over this defendant, then you run the risk of a Section 1983 lawsuit and the victim soon becoming the defendant.

RTC continues to post without any acknowledgment of his/her true stripes. Anonymous legal advice is questionable. Until RTC/Hoover/Grassy Knoll comes clean, his/her advice should be suspect.

There is nothing wrong with considering whether lies told during civil litigation could be prosecuted as perjury. Indeed, the Texas Court of Criminal Appeals is considering the reach of laws other than perjury into that realm. Whether a response to civil discovery would be sufficient to raise a perjury case is an interesting question. But it might be even easier to look at the tampering with government record provisions.

Our office has prosecuted several pro se defendants for filing lies in the course of a false claim of innocence. In those cases, the defendant's lie was objectively verifiable through contradicting sworn statements or through a voluntary confession.