The multi-functional phone helps them smuggle drug and pistols into jails and even communicate with each other to stage a mass breakout from jails.

A criminal syndicate boss reportedly issued orders to his men outside jail.

The phone also helps detainees expose jailers' maltreatment, defaming the United States styling itself a "champion of human rights".

In a bid to solve the problem, jamming and monitoring devices have been installed in jails. But it seems that they are not enough to put all of the several million detainees under surveillance.

Besides, the U.S. communication law does not allow blocking licensed frequency wave.

Another plan to solve the problem is to detect smartphones with the help of sniper dogs, but it is also viewed not to be a good idea.

Many Americans are of the opinion that an effective remedy is to sharply reduce the number of detainees.

But it is unlikely that criminals will be decreased in the United States, where all manners of social evil and injustice stalk.