Next, we walk over to the south end of grounds, the area that Siller says tends to be the most problematic. It's been better now that the midway is gone, but he says he still sees the most activity in this section. As we circle back to walk north along the rocks, another drunk and nervous woman awkwardly tries to flirt with him. We then spy a group of shady-looking teens sitting on the rocks.

Siller jokes that all teens look shady -- because they're teens, of course -- but he's still willing to bet that the kid drinking from the plastic Pepsi bottle has smuggled in alcohol. It turns out that he's 21, and the bottle actually contains soda, but both cops know the group is up to no good. They don't find anything, but they accomplish their mission. "They know we're here," says Siller.

Shortly after 9 p.m., we smell an obvious plume of marijuana wafting over the rocks, and like bloodhounds, Siller and Downey immediately turn to the right group of kids. As Siller begins to question a cocky 17-year-old, his friend flicks something into the lake. Now almost dark, it's a lost cause of the officers, who shine their flashlights into the water.

"Do you admit it yet or do we have to go find it?" asks a bemused Siller.

"Find what?" the kid asks innocently.

Siller asks to sniff his hand, which doesn't smell of pot. His friend, the one who threw something into the water, has quietly disappeared. We move on.

At this point, Siller asks me to identify someone I think is breaking the law. Not sure I'm up to the task, I still try to use their method of looking for someone appearing shifty or hiding something, but I can't sense anything. Finally, Siller sees three teenagers, not drinking, but immediately knows something is awry.

Siller searches one teen, while Downey searches the other. Something seems suspicious about these kids; both their eyes are dilated and glossy, and they seem too mellow in this situation. The officers find cigarettes and lighters, but no drugs. Meanwhile, the third friend has blended into the crowd and left -- again.

At this point, the officers use their discretion, since Summerfest is private property. They can't prove anything beyond underage smoking -- Siller says he plans to call the kids' parents later -- but he still escorts the pair from the grounds and warns them not to come back. In retrospect, Siller and Downey are sure that the third teen was the one with the drugs. But again, the pair has to pick its battles, and notably, the kids make no objections to being kicked out.

A Matter of Discretion

Close to 10 p.m., we stroll past the now-crowded Harley stage, and a visibly drunk and underage boy literally walks into us, holding two beers. Siller tells him to stop walking. At first, the kid tries to ignore the officers and keep going. But Siller grabs his shirt gently -- but firmly enough -- and cards him.

The boy is 18, and has just graduated from high school in West Allis. He says he "got the beers from some random guy." Siller kicks over his beers, grabs the back of shirt and starts to take him in.

To get back to the command post, we walk through the mosh pit at the Dropkick Murphys show. Wisely, none of the moshers elbow the cops, and gradually we weave through the crowd and sit down at the booking table.

The kid calls his mom on his iPhone and eventually hands it over to Silber, who explains that because he's 18, he doesn't have to release him into her custody -- but asks her if she'd like to pick him up, anyway.

While we wait for the mother, Downey fingerprints the boy and begins writing his ticket. Both Downey and Siller are a little rusty at writing tickets -- remember, this isn't their normal job.

The boy is now crying and is very apologetic. I ask him if he's drunk, though I know the answer. He says, yes, that he's had about four beers. He says he's acted very stupidly tonight.

He's losing any composure he had earlier, and asks if this ticket will jeopardize his full academic scholarship to college this fall. Now, Downey takes a soft and conciliatory tone, explaining that he's not going to jail. Downey recommends he saves his partying days for college and play it safe this summer. Downey is being much nicer than he needs to be.

And then the kid says something that changes his future tonight. He asks if his mom will get in trouble for buying him the beer.

Downey stops writing the ticket and asks him to explain. Apparently, if a parent buys her son a beer at Summerfest, it's not illegal. She just has to stay with him, which she did not. So, while a crime was and wasn't committed, it wasn't as serious as the kid trying to buy beers from a bartender or using a fake ID.

The boy says the reason he told the officers that he got the beer from the "random guy" was to cover for his mother. The officers share a glance with each other and void the ticket on the spot. They're going to let him go with a warning.

"Discretion is what separates good cops from great cops," says Siller as they release the boy to his appreciative mother.

"Every Point of Contact Makes an Impression"

I ask Siller to explain, and Siller turns the question around on me. He says he planned on asking me one important question, had I been able to identify a single underage drinker: "Would I have let him go?"

Since I wasn't responsible for finding someone to bust, I can only answer for the two people we did pick up tonight. Interestingly, I think I would've handled it exactly like the cops did.

The first guy was unapologetic and shifty, but the high school kid was reflective, remorseful and concerned about his future. Siller noted, too, that the boy was Hispanic -- and he says he personally works to dispel the myth that police officers unnecessarily hassle minorities. He explains out that every point of contact with the police is the opportunity to make an impression, and if this kid left Summerfest tonight believing that cops are here to help, well, then, letting him off the hook was worth it.

I say farewell to Siller and Downey at this point, left with my own impressions of the job they do. My contacts through OnMilwaukee.com have provided me with a number of experiences with the police -- though the Vice Squad, the Harbor Patrol, the DUI enforcement team, and now, the Summerfest patrol. Like always, it's professionally interesting and personally intriguing to step into their shoes for a shift, to understand why they make the decisions they do.

Is Summerfest safer because a few underage age drinkers and pot smokers got stopped Friday night? Probably not, at least not specifically. But knowing that rational, thoughtful cops are patrolling the grounds, on alert to handle bigger problems -- is especially impressive given the size and scope of the Big Gig and the volatile powder keg it could so easily ignite.