In some states, if you and your husband are estranged, you lose your right to inherit from him. This isn't the case in Alabama, as the state's legislative code is emphatic that unless you're actually divorced, you're still entitled to a share of his estate after he passes away.
Depending on the extent and details of your husband's estate, Alabama law provides that you're entitled to a homestead allowance and a family allowance even if you were living apart at the time of his death. If he attempted to write you out of his will after you separated, you can override this by claiming an elective share of his estate to which you are entitled despite what is in the will. Alabama's elective share is either one-third of his property, or the balance of his assets after the value of your own separate property is subtracted from the overall value of his estate. If your husband did not leave a will, your rights depend on whether his parents are living, whether he had children, and whether you are also the parent of his children. If he doesn't leave parents or children, you're entitled to his entire estate.
Whether you and your husband separated informally by simply moving into separate homes, or formally by obtaining a court-issued separation decree, you can inherit from your husband under Alabama law. A separation decree does not legally end your marriage; it just governs the terms of how you and your husband will live apart. As long as your marriage is not legally terminated by divorce, you're entitled to a share of his estate if he passes away before the divorce is finalized.