EXHIBIT 5.1



                        [LETTERHEAD OF DUANE MORRIS LLP]


      May 9, 2005


      Mitek Systems, Inc.
      14145 Danielson Street, Suite B
      Poway, CA 92064


      Ladies and Gentlemen:

      At your request, we have examined the Registration Statement on Form S-2
of Mitek Systems, Inc., a Delaware corporation (the "Company"), filed with the
Securities and Exchange Commission (the "Registration Statement") relating to
the registration under the Securities Act of 1933, as amended, of up to
5,300,000 shares of the Company's common stock, $0.001 par value per share (the
"Stock"), issued to certain selling shareholders named in the Registration
Statement (the "Shareholders") or issuable to such Shareholders pursuant to the
exercise of certain warrants to purchase shares of Common Stock (the
"Warrants"). The 5,300,000 shares of Stock include 1,060,000 shares that are
issuable upon exercise of the Warrants (the "Warrant Shares").

      As counsel to the Company, we have examined the proceedings taken by the
Company in connection with the issuance by the Company of the Stock and
Warrants, made such inquiries of certain officers of the Company and considered
such questions of law as we have deemed necessary for the purpose of rendering
the opinions set forth herein. For the purpose of the opinion rendered below, we
have assumed that in connection with the issuance of the Warrant Shares, the
Company will receive consideration in an amount not less than the aggregate
exercise price per share of Stock covered by such Warrants.

      We are of the opinion that all of the shares of Stock have been duly
authorized by the Company. In addition, we are of the opinion that the shares of
Stock when issued, including the Warrant Shares when such are issued and paid
for in accordance with the terms of the Warrants, will be legally issued, fully
paid and nonassessable.

      We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to all references to us in the Registration
Statement, the prospectus constituting a part thereof and any amendments
thereto.

                                                 Very truly yours,


                                                 /s/ Duane Morris LLP
                                                 ---------------------------
                                                 Duane Morris LLP