When law enforcement pulls me over for speeding, I have always been
asked "Do you kow why I pulled you over?" or "Do you know how fast you
were going?" Why? Why do they want to know if I know? Perhaps finding
out if I know is not the point of asking the question?  Is there
another motive?

Hello manofwar,

The comments below are all good answers, and I decided to answer this
from experience.

Quick Answer : Self incrimination. They want to get you to admit
something.

Each jurisdiction will argue to discredit this until they are blue in
the face, but here is what the University of North Carolina Legal
Office has to say about this:

North Carolina University
"When you are confronted by a law enforcement official— local cop,
State Trooper, ALE guy, or whatever- you do NOT have to answer their
questions."
http://www.unc.edu/student/orgs/sls/hotlegaltip12_00.html

Flex your Rights
"The first thing you should say to the officer is, Hello officer. Can
you tell me why I am being pulled over?"
http://www.flexyourrights.org/

My closest friend is a Police Officer in Queens, New York City. He
verified this information, and says funkywizard 'hit the nail on the
head'. He says the same things apply to many situations, but I'll save
that for myself, as I don't want people to start using my answer as a
'method to their madness'. (Laughing)

I found this answer to be humorously dangerous. (I like it :-) Use
this next one at your discretion -

"Absolutely. You've randomly selected me from the thousands of traffic
violators sharing this highway in order that I may be the next victim
of your ongoing ego-feeding power trip or you're a delusional control
freak with an unrealistic view of your role in bringing order to an
inherently disorderly world, probably the result of a chaotic or
abusive childhood, or you want to enforce your parochial, nay,
fascistic interpretation of the traffic code by forcing me to give up
my monkey chauffeur."
http://www.citybeat.com/2001-06-07/pseudo.shtml

Search strategy:

Self incrimination pulled over
://www.google.com/search?q=Self+incrimination+pulled+over

"Do you know why I pulled you over"
://www.google.com/search?q=%22Do+you+know+why+I+pulled+you+over%22

Thanks for the very interesting question!
SgtCory

seeing if your lying?

In my personal experience various "disciplinary" figures use this
method. For example, I recently got in trouble for over-using the
internet connection at college. Instead of simply coming out and
saying "hey you did this bad you!" they collected all the information
they needed, scheduled me to show up in their office for a meeting,
wouldn't tell me what the meeting was about until I got there, and
then asked me "ok what's going on". If I attempt to answer in a way
that makes me look good, I lose because they already know im Lying. If
I ask "could you be more specific" which is what I did the second time
something like this happened, they got pissy and shoved in my face
exactly what they were mad about. Really, I think this is just a way
to corner you and to see if you are lying. If you tell a story that
more or less jives with what they already know, they will be much
happier with you. However, they don't want to tell you what they
already know, because this would allow you to craft your lie to best
fit what information they already have.

Thus, two parts here from what I can tell. If they ask *you* first,
they can more easily tell if you are lying, because you cannot judge
ahead of time what they already know. Secondly, it lets them know how
truthful and cooperative you are going to be. If they did this in some
other order, they would have a harder time knowing if you are lying or
not.

One more thing. It is entirely possible they pulled you over for no
good reason, in which case they are hoping you will fib on yourself.
By not telling you everything they know, they may be trying to get you
to confess to crimes they have no knowledge about. For instance, if
they ask "do you know why I pulled you over" and you were speeding 100
miles an hour, and you respond as such, they may be like "oh i didnt
know that. you had a taillight out. but since you were speeding 100
miles an hour, heres another ticket". Whereas if you say you have no
idea but you were clearly going double the speed limit, they will not
be happy either.

All in all, I really think these tactics are to screw people over.

Here is one of my personal favorite story´s:

"The person I heard this from ("Al" in the story) swears that it
really happened. (And no, I'm not this "Mark" - you should be able to
figure out why I chose those names. :)

Two guys (we'll call them "Mark" and "Al") are out cruising. Mark is
driving, and they're on some out-of-the way roads. Mark is distracted
and doesn't see a stop-sign, and a few moments after he runs it they
hear a siren and see blue lights. Mark has never been stopped by the
police before, and gets really nervous.

MARK: OhshitwhatdidIdo? I wasn't speeding, was I? No, I wasn't
speeding. What'd I do what'd I do?

He pulls over, shaking like a leaf. The cop pulls in behind and walks
up to his window.

COP: You realize you ran a stop sign back there? 

MARK: [panicky] No, honest! I didn't see it! I didn't mean to run it!
I just didn't see it! Really!

COP: I'll need to see your driver's license. 

Mark pats his pants for a few seconds before remembering that he's
wearing shorts with no pockets. He looks around the car, finds his
wallet, opens it up, and starts frantically throwing things out of it
into the back seat. No license. He enlists Al's help, and together
they search the glove compartment, under the seats, behind the
cushions, front and back, to no avail. After ten or fifteen minutes of
searching, Al looks up and catches the officer's eye.

AL: You don't need to see his identification. 

COP: [without missing a beat] I don't need to see his identification.

AL: These aren't the droids you're looking for. 

COP: These aren't the droids we're looking for. 

AL: He may go on about his business. 

COP: You may go on about your business. 

AL: Move along. 

COP: Move along. 

At this point the cop turns around, walks back to his car, gets in,
and drives away.

Mark pulls out and makes it about 200 yards down the road. Then he
stops and just shakes for a few minutes, finally asking Al to drive"
http://www.comedycorner.org/69.html