Additional District and Session judge Shailendra Kumar also imposed a penalty of Rs 10,000 each on all the accused.
In case of failure to pay the fine, their sentence would be increased by one year. The victim's husband Shambhu Kumar Arya is among the 12 convicts.
Sanjoo Devi, 23, was strangled to death in Saristabad locality of Jehanabad district on November 24, 2008. The victim's brother had lodged a police complaint alleging that her in-laws used to constantly harass his sister for dowry.