My wife was recently involved in a traffic accident. A Mercedes had
cut in front of her at precisely the same moment that the traffic in
front of her came to a stop. The Mercedes rear-ended the car in front,
and my wife ended up rear-ending the Mercedes. Common sense would
indicate that the Mercedes driver is at fault for cutting in so close.
However, the insurance agent told my wife that according to the law,
the driver who hits another person's car from behind is automatically
at fault.

Superficially this law makes sense, since it's a driver's
responsibility to keep enough distance to the car in front so that
he/she can stop in time, no matter what. However, if somebody cuts in
too close in front of you, it shouldn't be considered your fault that
the car is too close.

My question is now, does the law (in California) really say that the
driver that hits another car from behind is always at fault? Or was
the insurance agent oversimplifying, or just not telling us the truth?
In what situations would the driver that cut in in front of the
rear-ending car be held responsible?

Hi tranquillion:

[Please bear in mind that Google Answers results are not intended to
substitute for informed professional medical, psychiatric,
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professional advice.]

Thanks for the interesting and challenging question. 

I'm not sure that your insurance agent is telling you the whole story
here. While it may be your insurance company's policy to say the
driver in the car behind is always at fault for a rear-end, that is
*not the law*.

In fact, the concept of "fault" in traffic accidents isn't really a
part of law in California. See the following for details:

Questions That Need Answering
URL: http://64.233.167.104/search?q=cache:feENq1Db_KwJ:www.spies.com/Forums/showthread.php%3Ft%3D215%26page%3D3%26pp%3D25+%22determining+fault%22+rear-end+california&hl=en
Quote: 
****************************
"Fault" as such isn't codified as law. For one thing, no law could
possibly anticipate all the possible variations in accidents. For
another, "fault" is a matter between *private* parties. The state
cares if you violate a law (including the Vehicle Code), but it
doesn't care who's "at fault" in a private dispute about a car
accident or a "slip and fall" or any other civil wrong, or tort.
Insurance companies offer to settle claims based on their (usually
accurate) estimate of what would probably happen if the case came to
(civil) trial--who would be found at fault, and for how much in
damages. And it's true that, by and large, people who get rear-ended
aren't seen as negligent, while those who rear-end them are. But the
circumstances vary from case to case , and there's also (in
California) a doctrine called "comparative negligence," which lets
juries determine, on the basis of the facts of the particular case,
whether *both* parties were at fault, and to what degree.
************************

So, basically the concept of "comparitive negligence", which has been
recently adopted in California, means that if push came to shove you
(or your insurer) could take this matter to court to get a
determination of how fault for the accident should be apportioned
between the two parties.

comparative negligence
URL: http://dictionary.law.com/definition2.asp?selected=256&bold=%7C%7C%7C%7C
Quote: "n. a rule of law applied in accident cases to determine
responsibility and damages based on the negligence of every party
directly involved in the accident. For a simple example, Eddie
Leadfoot, the driver of one automobile, is speeding and Rudy Airhead,
the driver of an oncoming car, has failed to signal and starts to turn
left, incorrectly judging Leadfoot's speed. A crash ensues in which
Airhead is hurt. Airhead's damage recovery will be reduced by the
percentage his failure to judge Leadfoot's speed contributed to or
caused the accident. Most cases are not as simple, and the formulas to
figure out, attribute and compare negligence often make assessment of
damages problematic, difficult, and possibly totally subjective. Not
all states use comparative negligence (California is a fairly recent
convert), and some states still use contributory negligence which
denies recovery to any party whose negligence has added to the cause
of the accident in any way. Contributory negligence is often so unfair
that juries tend to ignore it."

Of course, *proving* that the driver of the Mercedes was partially at
fault might prove very tricky, if not impossible:

Proving Fault in Vehicle Accidents
URL: http://cobrands.public.findlaw.com/motor_vehicle_accidents/nolo/ency/262D0D22-2CB9-4DF2-AFAF3F7CA3DFE1D8.html
Quote: "If someone hits you from behind, it is virtually never your
fault, regardless of why you stopped. A basic rule of the road
requires a vehicle to be able to stop safely if traffic is stopped
ahead of it. If it cannot stop safely, the driver is not driving as
safely as the person in front....Keep in mind, however, that even if
you have been rear-ended, in a few circumstances your own carelessness
may reduce your compensation under the rule of 'comparative
negligence.' A common example is when one or both of your brake or
tail lights were out, especially if the accident happened at night.
Another example is when a car had mechanical problems but the driver
failed to do all she could to move it off the road."

The difficulty in proving the other driver shares the blame is
probably why most insurance companies simply choose to behave the way
they do regarding rear-end accidents.

As far as under what situations would the driver that cut in in front of the
rear-ending car be held responsible - that would be up to a judge or
jury to decide, if it ever came to that.

This is perhaps not the most encouraging answer to your problem, but
at least it's let's you know what's what.

Search Strategy (on Google):
* "rear-end" accident "who's at fault" california
* "determining fault" rear-end california
* "comparative negligence" california
* "comparative negligence" rear california
* "comparative negligence" "rear end" california
* "comparative negligence" "rear end" -motorcycle california
* fault accident "codified as law"
* california "vehicle code" 

I hope this helps!

websearcher

IF witnesses agreed that the Mercedes tail-ended the other car first,
before your wife hit him, confirming reckless driving on his part,
that might bear in your favor.  But that is an IF and a MIGHT ...
It could go the other way, a claim that your wife hit him and forced
him to hit the other car...
Just a comment, and certainly no advice of any kind.

In Florida (I know that may not help very much) it doesn't matter
whose fault it is.  The insurance company of the car that rear-ends a
vehicle is always held liable.  Traffic citations are not always
handed out, but I have never heard of a person rear-ending someone
else (no matter the reason) not having their insurance held liable for
damages.  I think the only really important question is does it make
the cost of your insurance go up.