Why did Voldemort choose Narcissa to verify that Harry was dead?

Narcissa is a very valuable person for Voldemort, although the Malfoys fell into miscredit earlier in the book. It is shown at the beginning of Deathly Hollows, how valuable she was:

“I don’t understand you, Kreacher,” he said finally. “Voldemort tried to kill you, Regulus died to bring Voldemort down, but you were still happy to betray Sirius to Voldemort? You were happy to go to Narcissa and Bellatrix, and pass information to Voldemort through them. . . .”
_{*Deathly Hallows, Chapter Ten: Kreacher's Tale}

And she helped identifying Harry (though indirectly) when he got caught and brought to Malfoy Manor:

Through his puffy eyelids Harry saw Narcissa Malfoy scrutinizing his swollen face. Scabior thrust the blackthorn wand at her. She raised her eyebrows.

“Bring them in,” she said.
_{*Deathly Hallows, Chapter twentythree: Malfoy Manor}

But the decision whom to send to check in the end does not seem to be rational at all:

“You,” said Voldemort, and there was a bang and a small shriek of pain. “Examine him. Tell me whether he is dead.”
_{*Deathly Hallows, Chapter thirtysix: The flaw in the plan}

He might have probably -subconsciously- wanted a mother to check as a mother gave the protection to Harry (but he didn't know at that point). Or he just wanted to punish someone and Narcissa was the unlucky one to stand near him, we never learn to know the real reason.

And as we now know, she betrayed Voldemort out of the reason he might have probably thought she would be useful: The sorrow for her son at Hogwarts:

Hands, softer than he had been expecting, touched Harry’s face, pulled back an eyelid, crept beneath his shirt, down to his chest, and felt his heart. He could hear the woman’s fast breathing, her long hair tickled his face. He knew that she could feel the steady pounding of life against his ribs.
“Is Draco alive? Is he in the castle?”
The whisper was barely audible; her lips were an inch from his ear, her head bent so low that her long hair shielded his face from the onlookers.
“Yes,” he breathed back.
He felt the hand on his chest contract; her nails pierced him. Then it was withdrawn. She had sat up.
“He is dead!” Narcissa Malfoy called to the watchers.
_{*Deathly Hallows, Chapter thirtysix: The flaw in the plan}