See the 1996 Wisconsin Supreme Court case State v. Lohmeier for how an analagous situation was handled in Wisconsin. A driver was drunk, and two pedestrians were walking on the right side of the road instead of the left side (which is against Wisconsin statute 346.28.) The pedestrians were struck (some evidence showed that they had stepped into the traffic lane) and died.
According to the opinion:
...§ 939.14 provides that a defendant is not immune from criminal liability simply because the victim may have been negligent as well.
However, this rule does not mean that evidence of a victim's negligence is irrelevant in a criminal proceeding. It was relevant here to the affirmative defense, and it is often relevant on the issue of causation.
And another case is cited in which:
the victim's negligence was relevant to determining whether the defendant's intoxicated driving was a substantial factor in causing the victim's death.
This is important because the laws in question punish someone who "causes the death" of another by their intoxicated (or negligent) operation of the vehicle. According to the courts, if that wasn't at least a "substantial factor" in the death, you can't be guilty of vehicular homicide. It's really up to the jury to decide whether that's the case. In this case, the jury convicted, and the conviction was upheld by this decision.
You can make a plausible claim that the negligence inherent in drunk driving is not the cause of a particular accident if someone abruptly steps in front of the car (although the prosecution can argue that a sober driver might have been able to react to the situation.) But the negligence inherent in driving the wrong way will usually be the very reason the pedestrian steps in front - the pedestrian isn't expecting someone from that direction. So, in the case of a wrong-way driver, I think it is extremely likely that the driver would be found criminally negligent.