Sometimes it's luck. Sometimes it's skill.
In this investigation by one Las Vegas police unit, both factors played a part.
When Bohumil Capek walked out of a Vons grocery store last week after a failed robbery attempt, officers Shane Koboski and Jonathan Smith were in the parking lot waiting to arrest him, authorities said.
The officers had been staking out the store, one of several businesses identified by the Northwest Area Command's problem-solving unit as a likely target for Capek, a suspect in a string of robberies over a span of four days.
And they were right.
"We'll take a little luck, when we can get it," Lt. Jim Seebock said.
But don't discount the police work: Seebock said Capek's pattern, after a lot of research, was becoming obvious:
He always struck at about the same time, in the same area, stole the same brand of Parliament cigarettes and asked cashiers the same question: "Do you have a family?"
Police weren't throwing all their eggs in the Vons basket, however. Several other officers were staking out other stores that night, Seebock said.
Capt. Chris Jones, who oversees the Northwest Area Command, said predicting criminal behavior -- down to the location, time and date -- is extraordinarily tough.
"That's a very difficult thing to do," he said. "In my 19 years, I think we've done that three times."
As for Capek, he was booked at Clark County Detention Center on three counts of robbery with a deadly weapon and one count of attempted robbery.
In addition to the Vons at 7530 W. Lake Mead Blvd., Capek was accused of robbing a 7-Eleven at 7650 W. Charleston Blvd., an Albertsons at 1650 N. Buffalo Drive and a CVS at 8320 W. Cheyenne Ave.
He also attempted to rob a Walmart at 3615 S. Rainbow Blvd. hours before his arrest, police said.
Capek, who told detectives he needed money for his drug problem, probably never used a weapon, Seebock said.
When he was caught, Capek had needle-nose pliers in his pocket. But because he simulated having a gun, he was charged as if he did.
Capek has a lengthy criminal history in Nevada that includes arrests for domestic battery, possession of a controlled substance and three separate drunken driving incidents, the latest of which was July 28.