is it possible for law enforcement background investigators to read logs of your text messages even if they have been deleted? Say a person allegedly bought drugs and set up meets via texts but that had been deleted, can the BI contact your cell phone provider to give them the content of your text messages? If this is true are many Law Enforcement Agencies requiring applicants to sign a waiver allowing them to view emails, text, messages, social media, etc. Also if you delete all social media that you belong to before applying to a department does that come off as suspicious that you would be given an automatic dq?

If you are an applicant for the job, all of this is irrelevant.  A law enforcement agency will only do something like subpoena your phone records, internet records, etc.  if they had a strong criminal case against you and wanted to indict you for a serious crime.  As a job applicant, they will not do this.  There is not enough time, money, or care for any organization to do computer forensics on job applicants.

The background check, just like any security clearance background check, will only really reveal what you tell them (and what is on record, such as arrests and convictions).  If you have purchased illegal drugs in the past, were never caught, and nobody except for you knows about it, DON'T MENTION IT!  If you open the door, you are just digging a hole for yourself.  Keep your mouth shut.

No background check includes digging into an applicant's your social media.  They MIGHT decide to do some Google searches on you anyway for fun to see what info is public online about you, but that is it.  No need to delete your social networking accounts.  It is 2014 and almost everyone has some social networking site.  Just make sure your privacy settings are set so that not just anyone can see all of your info and pictures, and don't have any self-incriminating photos or messages posted, such being naked and drunk or puffing a bong during vacation, or a politically offensive rant (your background investigator, or job interviewer, may have a political bias).

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It should not, no. I know for my agency, they did ask if I "lived with/had frequent contact with any convinced felons", if so "what is their name", "what were they convicted of", and "how long ago was it" were included questions. I told them that I am around my uncle, convicted of several felonies in the 80s and he spent over 10 years behind bars. They did not care. What they would care about with your future son-in-law would be, for instance, him living with a registered sex offender.

-Anonymous Deputy