POWER OF ATTORNEY

Know all by these presents, that the undersigned hereby constitutes and
appoints John R. Cook, Phillip D. Torrence, John H. Castle, Kurt G. Miller,
Jaylen T. Johnson and Danice Chartrand, and each of them, with full power of
substitution and/or revocation, the undersigned's true and lawful attorneys-in
- -fact:

    (1) to execute for and on behalf of the undersigned, in the undersigned's
capacity as an officer and/or director of Southern Michigan Bancorp, Inc. (the
"Company"), any and all forms (including, without limitation, Form 3, Form 4
and Form 5) required or desired to be executed by or on behalf of the
undersigned in accordance with Section 16 of the Securities Exchange Act
of 1934, as amended, and the rules thereunder (the "Forms");

    (2) to do and perform any and all acts for and on behalf of the undersigned
which may be necessary or desirable to complete and execute any such Form and
timely file such Form with the appropriate governmental authority (including,
without limitation, the United States Securities and Exchange Commission) and
any stock exchange or similar authority; and

    (3) to take any other action of any type whatsoever in connection with the
foregoing which, in the opinion of such attorney-in-fact, may be of benefit to,
in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by any such attorney-in-fact on behalf
of the undersigned pursuant to this Power of Attorney shall be in such form
and shall contain such terms and conditions as such attorney-in-fact may
approve in such attorney-in-fact's discretion.

The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might
or could do if personally present, with full power of substitution or
revocation, hereby ratifying and confirming all that such attorney-in-fact,
or such attorney-in-fact's substitute or substitutes, shall lawfully do or
cause to be done by virtue of this Power of Attorney and the rights and powers
herein granted. The undersigned acknowledges that the foregoing a
ttorneys-in-fact, and each of them, in serving in such capacity at
the request of the undersigned, are not assuming, nor is the Company
assuming, any of the undersigned's responsibilities to comply with
Section 16 of the Securities Exchange Act of 1934, as amended.

This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms in accordance with Section 16
of the Securities Exchange Act of 1934, as amended, and the rules thereunder,
with respect to the undersigned's holdings of and transactions in securities
issued by the Company, unless earlier revoked by the undersigned in a signed
writing delivered to the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of October 21, 2002.

/s/ John H. Castle
John H. Castle