Joe was arrested for fraud. He was filing fake insurance claims and collecting money he did not deserve. The judge decided to put Joe behind bars for at least 2 years.
When the police realized that Frank had been driving while drunk, they put him behind bars for the weekend.
To put someone behind bars means to put someone in jail. Usually only the police or authorities are used as the subject because they have the authority to send someone to jail.
"To put someone behind bars" is a common idiom used by native speakers. Practical idioms like this can be learned from LSI Speaking books like "Speaking Transitions," which is used to teach the Level 4 Speaking/Listening classes at Language Systems schools. For more information please visit: www.languagesystems.com