As much as I would like to win every time (or frackin close), I can't.  Mostly I learned that years ago when I worked probation.  The judge has the final word.  Don't take it personal, sometimes the judge is soft, sometime they are want the person to have a chance.  Move on do your job.
I am sitting late Friday night, early Saturday morning, blacked out at a four way stop.  I am waiting for drunks to blow the stop sign or "chicken dinner" cars to come by.
I hear a car approaching.  The thump thump of the stereo, from over two blocks away, coming from behind me.  I see a Jeep approach.  It sees me and music stops and turn the street before  where my car is parked.
Great, I can just parallel it, because I believe it is trying to come out two blocks down on the main drag.  I expect it to pop out onto one of the side streets.  I search for the car.  But, there are no cars, no tail lights and no one around.  I backtrack where I saw the car turn.  There is a jeep parked in a lot near the back entrance to a bar.  There is male #1 in the passenger seat. Male #2  is near the back of the Jeep smoking. No one in the driver seat.
I drive up and ask if they were just coming down the street and parked. Male #2 "yes"
Are you the driver? Male #2 "no, he just went into the bar."
Both #1 and #2 smell like alcoholic beverages and are drunk.  Neither male say he was driving and their buddy Ryan, was driving.
Why did Ryan take off?  Male #2 "he was going to the store."
-There are only three things open in town and they are all bars.  Call you buddy tell him to get back here.- 
Male #1 and #2 are both suspended.  #1 is on probation and has a no alcohol clause.  So I contact the PO, who issues a detainer. One in custody.
#2 say his buddy, now named Mike, was driving, who he just bought the vehicle from.  I call Mike, who was asleep and sold the vehicle to #2 about 10 days ago.  #2 states there he did bought it, but another buddy was driving and he doesn't want to get him in trouble.  #2 says there is no insurance on the vehicle.
I list the charges that I will be charging #2 with if he doesn't start telling the truth.  I take the keys and take #1 to jail. I tell #2 I want him to get his "buddy" on the phone and I tell him to get back down here. #1 won't tell me what happened.  #1 wonders how long he will be in jail he is the car provider for his paralyzed uncle.  #2 promised to care for the uncle while #1 is in jail.
I make the trip to jail and back and meet with #2.  He has a new name, William.  I find the number for William Jr and Sr.  The phone is busy.  I am able to contact the grandmother who doesn't think either was in town.
I'm stuck.  I am pretty sure #2 was driving the car.  I am pretty sure I could arrest him for DUII.  I could also get him for DWS-V, Driving Uninsured, False Info, and what else I can think of....
BUT
I didn't see him operate the vehicle.  I didn't see him exit the vehicle.  I lost sight of the vehicle that it would be reasonable (but not frackin probable) another person could have got out of the driver's seat and ran.   With no driver I can't issue tickets, witthout a great defense (it would be thrown out by any good defense lawyer).
It bugs me.  I give him his keys back telling him the if I see it move it will be stopped and impounded.
The car stays there all night.  It's gone the next day.  I call William, he wasn't there #2 called him and asked him to lie, because #2 was driving.   William wanted no part.  I remind William how good a buddy #2 is.  #2 also called earlier bragging about driving home, out of the area.
I call #2.  I ask him how the drive home was.  #2 denies it.
-WRONG!  I know you were driving last night and drove home today-
"No, I didn't and I wasn't"
-WRONG.  If try to get people to lie to me you should at least get your story correct and not brag about it. -
"I wasn't driving."
-BULLSHIT!, So why should call the local PD and tell them not to arrest you and take your car?
"WHAT?! I...."
click, I hang up.  he thinks he is deep shit.  I call the local PD and request a call from an officer.
-Hey can you go to 123 S. Street and see if vehicle #123TYR is there?-
"Hey this Dpty. Zues. I am at 123 Street and the vehicle is there.  Whats up?"
I explain the situation and give him the guys information.  I ask for a favor watch the car, the house and guy. If he could lay some paper on the guy it would make my week.
 "no problem, I am a traffic officer, I'll get it down.
-Thanks, let me know if you hit pay dirt.
I explain it to another officer who agrees I could arrest and cite him, but it would be weak at best. 
I run into the cousin of male #1.  He heard what happened.  I point out what a good buddy #2 was to him and how #1's uncle won't have anybody to look out for him, or how I probably wouldn't have paid attention to #1 if I was able to prove #2 was driving.  The cousin states #2, even called and bragged to him.
What I know and what I can prove...two different things.
The irony......I was offered a job in the city where #2 lives.  Would it be wrong to introduce myself?