Does anyone have authority that supports allowing an officer to get down off the stand to observe the Defendant's eyes to see if there's resting or physiological nystagmus present? Authority to perform full blown HGN? I've heard you can do it but can't find a case...

I haven't done any research recently to see whether there are some new cases, but here are a few:

Martin v. State, 97 S.W.3d 718 (Tex.App.---Waco, 2003)(pet. ref'd.) (holding that the HGN is nontestimonial; this case focused on the roadside investigation but made the same claim, that the HGN violated the defendant's privilege against self-incrimination. Citing Gassaway v. State, 957 S.W.2d 48, 51, it states "...the performance of field sobriety tests is not compulsive in violation of one's right to be free from self-incrimination when it does not make an express or implied assertion of fact."

Specifically as it relates to your issue of in-court HGN demonstrations on the defendant, there are a couple of non-published opinions:

Vasquez v. State, 2005 WL 2659941 (Tex.App.---Dallas, 2005) ("...appellant complains that compelling him to submit to the in-court HGN test violated his privilege against self-incrimination. ... he argues that allowing the jury to compare the different HGN test results was the equivalent of compelling him to testify against himself. ... The physical information sought was the same for the two tests; the only difference was the result. ... Because physical results of an HGN test are not testimonial, the trial court in this case did not abuse its discretion in overruling appellant's objection that the in-court test violated his privilege against self-incrimination."

Blassingame v. State, 1996 WL 482950 (Tex.App.---San Antonio, 1996)
"...appellant contends that the trial court erred by ... (3) forcing the appellant to perform a field sobriety test in the courtroom ... Evidence of the ability of a defendant to perform field sobriety tests when not intoxicated is highly relevant and probative evidence for a jury who must determine beyond a reasonable doubt whether a defendant was intoxicated ... field sobriety testing in which a defendant's physical characteristics are displayed is not testimonial."

You can also point out to the court that old defense tactic of suggesting to the jury that "most people can't even do those tests sober" and argue that this is the only test that you can't fake not being able to do while sober (and the only one that you can't mask the effect of alcohol when intoxicated).

Hope these help you get started.

I don�t believe there�s a case directly on point as far as doing it in court. However, there are cases that say that HGN is not testimonial and that getting a Defendant to perform HGN does not violate the 5th Amendment. Some of those cases are Martin v. State, 97 S.W.3d 718 (Tex. App. Waco 2003), and Gassaway v. State, 957 S.W.2d 48 (Tex. Cr. App. 1997).

If it ain�t testimonial and doesn�t violate the 5th then there�s absolutely no legal reason in the world why you can�t compel a Defendant to do it in court. ESPECIALLY when it�s done in response to a defense attorney crossing your officer about people having �natural nystagmus�.

WTF??? Why are my apostraphes and quotation marks showing up as question marks??? Stupid computer.

BTW, I've done this a few times and, as yet, have not had a defense attorney appeal on that issue.

Trevor-

I've forwarded you a motion in liminie that I have filed in DWI cases. I've used it essentially to put the defense attorney on notice that if they kick down the "natural nastagmus" door then I intend to walk right through it. To this point, I've not yet had a defense attorney invite me in...

And oddly enough, I have never had a defendant who actually had medical records that documented a visible "natural" nystagmus (yes, I am aware all nystagmus is natural). Defense attorneys just throw that in their questioning of the officer to try to raise reasonable doubt, but when they are called on it, they get offended.

And, stranger still...in the times I've had officers do HGN on the Defendant in court I've never had one that actually had natural nystagmus. I've been REALLY worried they would because...well...let's face it...some of these trials take place pretty late in the day (like 9:00 or 10:00 am) and there's a good chance the Defendant will be drunk.

We had a plea bust a few months ago because after the defendant got up to probation the PO realized he was intoxicated. A trooper brought up a PBT and the guy blew a .07 at 9 AM.

Thanks y'all, this stuff will help immensely.