U.N. evidence that could show whether chemical weapons were used in Syria will head to a lab Monday, but the answer may just be a formality.

The American president has already said there’s no doubt Syria’s government killed hundreds of civilians in a chemical weapon attack. Independent tests have revealed “signatures of sarin gas” in blood and hair samples from Syria, Secretary of State John Kerry said.

President Barack Obama wants Congress to sign off on limited strikes on Syrian targets — but some lawmakers bristle at the idea of getting ensnared in another overseas conflict.