
311 S.E.2d 318 (1984)
VANCE TRUCKING COMPANY, INC. and Myrtle N. Walker, Administratrix of the Estate of Horace Hobart Walker
v.
Allen Ross PHILLIPS, Ed Kemp Associates, Inc. and Charles Jennings George, Jr., Allen Ross Phillips and Kemp Associates, Inc.
v.
VANCE TRUCKING COMPANY, INC. and Myrtle N. Walker, Administratrix of the Estate of Horace Hobart Walker.
No. 8314SC93.
Court of Appeals of North Carolina.
February 7, 1984.
*319 Biggs, Meadows, Batts, Etheridge & Winberry by M. Alexander Biggs, Rocky Mount, for plaintiffs/defendants appellants, Vance Trucking Company, Inc. and Myrtle N. Walker.
Biggs, Meadows, Batts, Etheridge & Winberry by D. Royce Powell, Rocky Mount, for plaintiffs/defendants cross-appellees, Vance Trucking Company, Inc. and Myrtle N. Walker.
Haywood, Denny & Miller by George W. Miller, Jr., Durham, for appellee, Charles Jennings George, Jr.
Smith, Moore, Smith, Schell & Hunter by Bynum M. Hunter and Alan W. Duncan, Greensboro, for defendants-appellees and cross-appellants, Alan Ross Phillips and Ed Kemp Associates, Inc.
VAUGHN, Chief Judge.
On appeal, plaintiffs and defendants, Phillips and Ed Kemp Associates, set forth *320 several assignments of error with respect to errors allegedly made by the trial court. Since none of plaintiffs' assignments of error relate to the liability of defendant, George, we affirm that part of the jury verdict finding no liability as to defendant, George.

Defendants' Contentions
At trial, a licensed breathalyzer operator testified that three hours and fiftyfive minutes after the accident, defendant, Phillips, had a blood alcohol level of .07% by weight. A medical pharmacologist testified that in his opinion, defendant's blood alcohol level at the time of the accident would have been .13% by weight. Defendants now contend that this testimony should have been excluded since the results of a breathalyzer test and expert testimony relating thereto are inadmissible and compromise the rule against cross examination regarding a criminal conviction or acquittal in a civil action. Another panel of this court has already settled this question to the contrary. See Trucking Co. v. Phillips, supra. We feel, as did the trial judge, that under the doctrine of the law of the case, the testimony in question was admissible at this trial. See Hayes v. Wilmington, 243 N.C. 525, 91 S.E.2d 673 (1956).
Defendants also contend that the judge's charge to the jury was improper in that it set forth a rebuttable statutory presumption that a person with a .10% or greater blood alcohol level is intoxicated. While we agree with defendants that the presumption of intoxication created in G.S. 20-139.1 relates only to criminal actions, we, nevertheless, find no merit in defendants' contention. See Wood v. Brown, 20 N.C.App. 307, 201 S.E.2d 225 (1973), later appeal, 25 N.C.App. 241, 212 S.E.2d 690, cert. denied, 287 N.C. 469, 215 S.E.2d 626 (1975). The trial judge charged, in pertinent part:
The motor vehicle law provides that it is unlawful for any person to operate a vehicle upon any highway when the amount of alcohol in his blood is 0.10 percent or more by weight.
Driving with an amount of alcohol in the blood of 0.10 percent or more by weight is negligence within itself.
However, a finding of such negligence does not establish a causal connection between it and the collision. The driver's condition, operating a vehicle with an amount of alcohol in his blood of 0.10 percent or more by weight, must have caused him to violate some other rule of the road and to operate his vehicle in a manner which was a proximate cause of the collision.
If you find, by the greater weight of the evidence, that Alan Ross Phillips was negligent in that he operated a vehicle while the amount of alcohol in his blood was 0.10 percent or more by weight, then you would consider this negligence in determining whether he was capable of maintaining proper control of this vehicle in the same manner as a reasonably careful and prudent person would have done under all of the circumstances then existing.
The above instruction created no presumption of intoxication and was in accordance with recognized law. A violation of a statute like the one herein that imposes a duty for the protection of others constitutes negligence per se. Lutz Industries, Inc. v. Dixie Home Stores, 242 N.C. 332, 88 S.E.2d 333 (1955).
After trial, plaintiffs moved for a new trial and submitted affidavits of two jurors to support their motion and show the materiality and prejudicial effect of the trial court error in excluding the testimony of Mr. William Wallace regarding the asphalt he found in the Pinto's bumper.
No evidence may be received that shows the effect of any statement, conduct, event or condition upon the mind of a juror or the mental processes by which the verdict was determined. See State v. Cherry, 298 N.C. 86, 257 S.E.2d 551 (1979), cert. denied, 446 U.S. 941, 100 S.Ct. 2165, 64 L.Ed.2d 796 (1980). Although the trial court erred by receiving the affidavits of these jurors, such error was harmless. The *321 trial court denied plaintiffs' motion for a new trial. We have not considered such affidavits on appeal.
Defendants lastly contend that the trial court erred in not granting their motions for a directed verdict at the close of plaintiffs' evidence or at the conclusion of all the evidence. In Trucking Co., supra, another panel of this court held that, with substantially similar testimony, the trial court erred in directing a verdict for defendants at the close of plaintiffs' evidence. We are bound by this decision under the doctrine of the law of the case. See Hayes v. Wilmington, supra.

Plaintiffs' Contentions
Plaintiffs first contend that the trial court erred by excluding the testimony of William Wallace pertaining to asphalt found in the bumper of defendant's vehicle. Realizing the consequences of our holding, we, nevertheless, agree with plaintiffs' contention. The doctrine of the law of the case overrides our hesitation to subject the parties to a fourth trial. In Trucking Co., supra, plaintiffs had excepted to several of the trial court's rulings excluding the testimony of Mr. William Wallace. The panel deciding the case found merit in the exception. Specifically, it held the following trial court ruling to be in error:
COURT: Now, ladies and gentlemen, the Court allows the defendant Phillips' motion to strike all of the testimony of the witness with respect to his observation of a tear shaped gouge in the pavement. You may not consider any of his testimony in that respect. You must disabuse your minds of his description of the so-called "gouge" that he saw. You must disregard and disabuse your minds of his testimony concerning the location of that gouge or mark in the pavement. You must disregard and disabuse your minds of his testimony concerning his visual comparison of the material that he has heretofore described as asphalt and rock on or about a bumper guard that he was in Greensboro or near the Ford automobile that he has described with the composition of the surface of Interstate 85 at the place that he has testified that he saw a "gouge" mark. None of that evidence, none of that testimony may be given any consideration by you. It is ordered stricken by the Court as being legally incompetent for your consideration. Pass to the next matter.
The trial court committed reversible error by excluding testimony another panel of this court specifically held to be admissible. Trucking Co. v. Phillips, supra.
Plaintiffs also contend that the trial court erred in bifurcating the trial as to the issues of liability and damages. The trial judge has discretion, under G.S. 1A-1, Rule 42(b) to sever issues for trial in order to further convenience or avoid prejudice. On remand, if the trial judge exercises such discretion, we recommend that he enter findings and conclusions that will establish the appropriateness of severance. See Wallace v. Evans, 60 N.C.App. 145, 298 S.E.2d 193 (1982). It seems to us that to try all issues in the next trial would not present a suit of unmanageable size and would tend to lessen the already protracted delay in the resolution of this controversy.
Reversed and remanded for proceedings not inconsistent with this opinion.
HILL and EAGLES, JJ., concur.
