COLUMBIA, S.C. — The lawyer for a state senator who authorities say converted campaign donations into personal cash is trying to get his charges dismissed by going after the laws used in recent years to convict several South Carolina sheriffs and lawmakers.

Defense attorney Rose Mary Parham attacks South Carolina’s two separate types of misconduct in office charges in a court filing Thursday. One is based in statutes passed by lawmakers, while the other is based in common law — the principles and legal customs that link the state to its colonial past.

In dense court papers that among other things cite a law passed in 1829, Parham said prosecutors chose to use both laws against state Sen. John Courson because the common law charge allows for an indicted lawmaker to be suspended while awaiting trial, putting pressure to resolve the case.

The legal principles in both charges are similar, so the indictments against Courson violate his constitutional rights to not be tried for the same crime twice. Also, the law passed by legislators nearly 200 years ago should have eliminated the common law misconduct in office charge, Parham wrote.

The charges also call for different punishments, so Parham said any sentence should be limited — in event of a conviction — to a year in jail and a $1,000 fine instead of the 10 years in prison possible under one of the charges.

Courson is also charged with using campaign donations for personal expenses. Prosecutors said the Republican lawmaker who has served 33 years in the Senate gave political consultants $248,000 in donations and received back nearly $133,000 for himself.

The prosecutor handling the case, David Pascoe, has said he won’t comment on the case except in court and in his filings.

Prosecutors in other criminal cases involving sheriffs and legislators have charged them with both kinds of misconduct in office, and several of those cases have been resolved with guilty pleas to just one of the counts. The laws essentially accuse public officials of not performing their job duties or of using their jobs for personal gain either because of evil intent or dishonesty.