Additional Sessions Judge Surendra Prasad Yadav held Sadhna Singh's husband, Ashok, father-in-law, Indra Bahadur, and Shiv Kumar Shukla guilty yesterday of hatching a conspiracy to kill her.
Two others-- Ram Shankar and Vinod -- were also handed life term for her murder, prosecution sources said.
During investigations it was found that Singh's in-laws were not happy with her as she had given birth to two daughters, and wanted to remarry their son.
Singh, a Shiksha Mitra, was in school in Sohna village when the two motorcycle-borne assailants shot her dead on May 11, 2010.