My private-sector employer just found out I have a felony record in another state from 25 years ago.
Employment law questions are very fact specific. One small fact can change the entire result. Here are some background points that might help. First, consider getting your criminal record sealed if possible. This can only protect you in the future. Because the crime was prosecuted in another state, you likely have to look to see what the other state's rules are to seal.
In Massachusetts, you can request to seal many -- though not all -- misdemeanor cases after a 5 year waiting period and many felony cases after a 10 year waiting period. Generally, the clock starts ticking the date of conviction (the date you were found guilty) or released from incarceration, whichever is later. That said, every time you are convicted or incarcerated, the clock re-starts, adding another 5 years for a misdemeanor, and 10 years for a felony. Also, if it was a juvenile case, the rules are different, so check those in the state you were convicted in, too. To see what your Massachusetts criminal record / Criminal Offender Record Information (CORI) looks like (if any), you can go here (register as an individual).
Prior to questioning you about your criminal history or terminating you (or making some other "adverse decision") based on your criminal history, Massachusetts employers who are in possession of your criminal history records must provide you with a copy of the criminal record they have of yours. If the employer is conducting five or more CORI investigations annually, they must have a written CORI policy. Ask for a copy of it. Look specifically, and/or ask specifically, for the policy regarding the potential for "adverse action" (termination, etc.) based on criminal history records. Know that blanket firing (or hiring) policies that reject all workers with criminal records violate Title VII of the federal Civil Rights Act of 1964 unless the employer can show it is necessary for the business to do so or a particular law makes the person ineligible for the job.
The Equal Employment Opportunity Commission (EEOC) is the federal anti-discrimination agency that enforces federal Civil Rights Act. Factors they suggest an employer should consider before taking action include the age of the offense, the nature and seriousness of the offense, the age of the person at the time of the offense and completion of the sentence, rehabilitation efforts, success in the same job without incident after the offense, and the relationship between the type of offense and the job. See the EEOC's 2012 guidance on this issue is here or file a complaint -- called "a charge" -- with the EEOC here.
If you have questions related to criminal background checks by Massachusetts employers, contact me.