Depends. If the distribution was from a pre-tax IRA account, it is generally taxable. If it was from an after-tax account (or contained some after tax funds) that would be indicated in Box 5 of the 1099-R. If the IRA belonged to a civil employee, that should be indicated in the Federal 1099-R entry
Since Maryland starts with the Federal AGI, any taxable portion of a 1099-R distribution would show on Form 502, Line 1d.
Here's more info on Maryland Inherited IRA's.
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