Four now-former Knox County school bus drivers that allegedly used electronic devices while behind the wheel face mandatory 30-day jail terms if convicted under a tough new law.

They are charged via recently unsealed grand jury presentments under a state law passed following the death of two Sunnyview Primary School students and a teacher’s aide in Knox County in December 2014 caused by a driver who was texting while driving.

The quartet of drivers are accused in separate incidents of using electronic devices — the exact nature of which hasn’t been revealed yet — during Knox County Schools’ spring semester.

The cases are Knox County’s first legal test of that law, and the second in the state. A Hamilton County grand jury in March leveled the charge — along with vehicular homicide — in a fatal school bus crash in Chattanooga in December 2016 that killed six children.

Read more from our news partners at the Knoxville News Sentinel.