Someone brought up needing to confess to it for a lie detector test for a defense job.

First of all for the 8,000,000 time people need to stop calling it a lie detector ffs. It's a polygraph and it's sole purpose in clearances is to focus on who they should investigate to justify their budget. It's either that or at random. If if you personally believe it's random then you can still be happy as that's the other option.

 Second, at least in the US (yes I know this is UK), they don't give a fuck about minor crimes like this. they want to know about federal level felonies and serious crimes. They would laugh at you for reporting this and maybe make a note in the file so people in the future could also have a chuckle. If you are ever in a scenario to get this type of job you'd listen very carefully to the question and answer only exactly what they ask. They really, really don't want you to wonder down some random fucking path and cause a ton of extra paperwork that won't matter.