Exhibit 5.1


                       [Haynes and Boone, LLP Letterhead]

August 26, 2005


Integrated Security Systems, Inc.
8200 Springwood Drive, Suite 230
Irving, Texas 75063

Ladies and Gentlemen:

         We have acted as special counsel to Integrated Security Systems,  Inc.,
a Delaware corporation (the "Company"), in connection with the issuance of up to
5,723,077  shares of the Company's  common stock, par value $0.01 per share (the
"Common  Stock"),  plus an indeterminate  number of additional  shares of Common
Stock issuable to prevent dilution resulting from stock splits,  stock dividends
or similar events,  to be sold by Laurus Master Fund,  Ltd. (the "Shares").  The
Shares,  which include:  (i) up to 4,000,000 shares issuable upon the conversion
of convertible  promissory  notes and (ii) up to 1,723,077  shares issuable upon
the  exercise of a warrant,  are being  registered  pursuant  to a  Registration
Statement  on  Form  SB-2  (as  amended  or  supplemented,   the   "Registration
Statement")  filed  with  the  Securities  and  Exchange  Commission  under  the
Securities Act of 1933, as amended (the "Securities Act").

         In connection therewith, we have examined and relied upon the original,
or  copies  certified  to our  satisfaction,  of (i) the  Amended  and  Restated
Certificate of  Incorporation of the Company,  as amended;  (ii) the Amended and
Restated  Bylaws of the Company;  (iii) the minutes and records of the corporate
proceedings  of the  Company  with  respect  to the  reservation,  issuance  and
registration by the Company of the Shares;  (iv) the Registration  Statement and
all exhibits  thereto;  and (v) such other  documents and instruments as we have
deemed  necessary  and advisable  for the  expression of the opinions  contained
herein.

         In making the foregoing  examinations,  we have assumed the genuineness
of  all  signatures,  the  authenticity  of  all  documents  submitted  to us as
originals, the conformity to original documents of all documents submitted to us
as certified or photostatic copies thereof and the authenticity of the originals
of such latter documents.  As to all questions of fact material to this opinion,
where such facts have not been independently established,  and as to the content
and form of certain minutes, records, resolutions or other documents or writings
of the  Company,  we  have  relied,  to the  extent  we have  deemed  reasonably
appropriate,  upon  certificates  of an officer of the Company and  governmental
officials.

         Based  upon  and  subject  to  the  foregoing   and  the   limitations,
qualifications,  exceptions  and  assumptions  set forth  herein,  we are of the
opinion that:

         1.    Upon the issuance of Shares to be issued upon the  conversion  of
promissory  notes or the  exercise  of a warrant,  such Shares  (when  issued in
accordance  with the terms of such  promissory  notes or  warrant)  will be duly
authorized, validly issued, fully paid and non-assessable.

         We hereby  consent to the  filing of this  opinion as an exhibit to the
Registration  Statement  on  Form  SB-2  filed  by the  Company  to  effect  the
registration  of the Shares under the Securities Act and to the reference to our
firm under the caption "Legal Matters" in the prospectus  constituting a part of
the Registration Statement.


                                                   Very truly yours,

                                                   /s/ Haynes and Boone, LLP

                                                   Haynes and Boone, LLP