I-94 overstay. How do they know?

[DifferentT]

there are cases when people were leaving the US with overstayed visa without their I-94 being submitted (for whatever reason) and then succesfully got a new one to come back.

Q: When applying for a new visa how do consulate people know if that visa was overstayed? Assuming of course there were no stamps in passport when leaving, no fingerprints taken etc.

 

[Concerned4us]

Unless and until I-94 is returned, the holder is assumed to be in the US. It then becomes necessary to prove date of leaving. Not returning the I-94 will not hide an overstay.

 

[Triple Citizen]

Flight manifests also record passenger movements.

Q: When applying for a new visa how do consulate people know if that visa was overstayed? Assuming of course there were no stamps in passport when leaving, no fingerprints taken etc.