LONDON — The son of Dawn Sturgess, a British woman fatally poisoned by a nerve agent discarded in a residential area by Russian intelligence officers, on Sunday asked President Vladimir V. Putin to allow British investigators to question the men presumed responsible, telling Mr. Putin, “I am appealing to you as a human being.”

“Allow our officers to question these men about my mother’s murder,” he urged Mr. Putin on the anniversary of the nerve agent attack, according to excerpts from a letter published in The Mirror. “The least she deserves is justice.”

Ms. Sturgess, 44, and her boyfriend, Charlie Rowley, 45, were collateral damage in the attack on Sergei V. Skripal, a former Russian spy who had been resettled in Salisbury, a quiet city in southern England. Since Ms. Sturgess’s death, Russian officials have repeatedly made light of the episode. In December, the state-run television network RT sent chocolate replicas of Salisbury Cathedral as holiday gifts.

On Sunday, Ms. Sturgess’s 20-year-old son, Ewan Hope, addressed Mr. Putin directly.

“He needs to show he’s capable of showing some humanity to our family,” he said. “I would ask him to imagine how he would feel if he was in my shoes.”