Exhibit 5.1


                       [Haynes and Boone, LLP Letterhead]

April 8, 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
85,307,479  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  the  selling  stockholders  named  in the
prospectus  constituting a part of the  Registration  Statement  (defined below)
(the "Shares").  The Shares, which include: (i) up to 12,086,821 shares issuable
upon the conversion of convertible promissory notes, (ii) up to 1,522,154 shares
issuable upon the exercise of warrants, (iii) up to 190,000 shares issuable upon
the conversion of the Company's Series A Convertible Preferred Stock, (iv) up to
706,250  shares  issuable  upon  the  conversion  of  the  Company's   Series  D
Convertible  Preferred Stock, and (v) up to 70,802,254 shares that are currently
outstanding,  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
(file no. 333-122849).

         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  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.     The currently  outstanding  Shares are duly authorized,  validly
issued, fully paid and non-assessable.

         2.     Upon the issuance of Shares to be issued upon the  conversion of
promissory  notes or preferred  stock, or the exercise of warrants,  such Shares
(when issued in accordance  with the terms of such promissory  notes,  preferred
stock or  warrants)  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 of 1933, as amended,  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




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