The Law:

Felons on probation, in prison, or on parole cannot vote. Anyone convicted of murder, manslaughter, certain sexual crimes, or offenses against offices of public administration such as bribery will remain disfranchised after completion of sentence. Others who have completed their sentences can either seek a pardon or wait five years from completion of sentence for their rights to be restored. Persons convicted of a misdemeanor for certain election-law violations are prohibited from voting for ten years following completion of sentence.

Getting Your Vote Back:

http://www.sentencingproject.org/pdfs/rights-restoration/Delaware.pdf