Today's sentences for the March blast are the most severe in a series of recent court action against suspects charged with attacks and alleged plots to topple the Sunni monarchy in the strategic kingdom, which is home to the US Navy's 5th Fleet.
Bahrain's Shiite majority has led a more than two year uprising seeking greater political rights. The verdicts are likely to stir more clashes.
The lawyer, Mohammad al-Tager, says the four suspects were convicted of the roadside bombing that wounded a worker when it missed its alleged target.