Let's assume for a few minutes that Robert Cowart really is incapacitated in some way by a stroke or other physical problems. I'm aware that some people have expressed doubts about this on postings at pressdemocrat.com and other online forums, suggesting that the man accused of running down bicyclist Steve Norwick and then fleeing the scene is putting on an act to elicit sympathy. But let's put aside those doubts and assume that the frail, confused and nearly helpless 68-year-old who appeared in court on Wednesday is the real deal.

And if that is the case, why in hell was he driving his pickup truck on Petaluma Hill Road last Friday?

According to people who were in Judge Robert LaForge's courtroom on Wednesday, Cowart's physical condition was "shocking." The man accused of slamming his Dodge pickup into Norwick five days earlier was barely able to walk in the courtroom. His lawyers steered and steadied him as he faced the judge. As he was helped into a wheelchair after a brief hearing, someone placed Cowart's hands in his lap before he was wheeled away, according to staff writer Mary Callahan's account.

Cowart's attorney, George Boisseau, told the court that his client recently suffered a stroke that may be impairing blood flow to his brain. Boisseau did not say when the stroke happened.

But again, for the sake of argument, let's assume that the Cowart who showed up in court on Wednesday was the same Cowart accused of driving the truck that mowed down Norwick on Friday.

You have to ask how he was able to drive in that condition. But the more important question is: Why?

Why, if he has a support network that includes a wife and two sons — as his lawyer claimed in arguing against higher bail — did that network allow him to drive in that condition? Why, if doctors recently treated him for a stroke that left him so incapacitated he can barely walk, did those doctors not take action to keep him from getting behind the wheel of a motor vehicle? Why, if he regularly stops into a local store to buy milk on his way to work, as he did shortly after Norwick was knocked off his bicycle and left lying gravely injured in a roadside ditch, did not some clerk or customer recognize that this was not a man capable of piloting a pickup, and try to stop him from doing so?

I'm not trying to shift the blame away from Cowart. If he truly is the man whose pickup crashed into Norwick, and who then drove away from the scene without stopping, then the blame for the crime is his.

But, if he was in the same shape last Friday as he was in court this week, the net of responsibility may be cast a bit wider than that of the blame.

California only requires us to renew our driver's licenses once every four years. If you're younger than 70, you can renew by mail — no written test, no eye test, just a signature and a check.

That leaves the rest of us with some responsibility to keep an eye on each other.

If we know someone is acting in a way that represents a danger to himself or others, such as a stranger waving a gun or a relative threatening to hurt someone, we're likely to take action. Maybe we'll try to reason with the person or try to take the weapon away or, when necessary, call the police.

We know instinctively that we must act.

We should also act when the potential weapon is a car.

To act in this situation is not as instinctual as when someone is behaving aggressively. A person who is incapable of safely operating a motor vehicle isn't usually belligerent or aggressive. He or she is usually just incompetent.

But he or she is still dangerous.

It's not always an easy call. When is your mother, or father, or spouse no longer safe behind the wheel? And, when that time comes, how do you convince her it's time to give up the keys?

I don't have an easy answer to that question. I confess that when I started having doubts about my mother, who lived 1,000 miles away, I took the easy way out and let my sister deal with it.

But, going back to Robert Cowart, the decision should have been easy for anyone who saw him in the condition he was in when he showed up in court on Wednesday. And, if that truly was his condition last Friday, it also should have been easy to simply take away his keys. He appeared to be in no condition to resist, just as he appeared to be in no condition to drive.

But what if he's a stranger you see out in the community, or a customer who stops into your store? What can you do then?

If he's having a hard time standing or walking, and you see him get behind the wheel, you do the same thing you'd do if he was waving around a gun: Call the cops.

Seriously, we should all be willing to do this. A motor vehicle in the wrong hands is just as deadly as a firearm in the wrong hands. The person wielding the weapon needs to be stopped.

It's not often so cut-and-dried. The loss of driving ability doesn't usually happen as if some switch is flipped and a driver goes from competent to incompetent overnight. Making a decision to intervene, to deny a loved one the freedom of driving a car, can be agonizingly difficult.

But, in Cowart's case, it should have been a no-brainer — if he was in as bad a shape last week as he appeared to be this week. And if someone had prevented him from driving on Petaluma Hill Road last week, both Cowart and Norwick would be better off today.

That's something all of us should keep in mind when we start to wonder if Dad ought to still be driving to the grocery store.

The California DMV has a form that can be submitted anonymously requesting "re-examination" of a driver suspected of no longer being capable of safely operating a vehicle. It is available at http://www.dmv.ca.gov/forms/ds/ds699.pdf.

(Chris Coursey's blog offers a community commentary and forum, from issues of the day to the ingredients of life in Sonoma County.)