Exhibit 5.1
                                                                     -----------


             [Sheppard, Mullin, Richter & Hampton LLP Letterhead]


June 24, 2003


National Technical Systems, Inc.
24007 Ventura Boulevard, Suite 200
Calabasas, California 91302

            Re:   Registration Statement on Form S-8
                  ----------------------------------

Ladies and Gentlemen:

            We have acted as  special  counsel to  National  Technical  Systems,
Inc.,  a  California  corporation  (the  "Company"),   in  connection  with  the
registration on Form S-8 (the "Registration Statement") under the Securities Act
of 1933, as amended,  of 1,000,000 shares of the Company's common stock reserved
for issuance under the National Technical  Systems,  Inc. 2002 Stock Option Plan
(the "Plan").

            This opinion is being furnished in accordance with the  requirements
of Item 8 of Form S-8 and Item 601(b)(5)(i) of Regulation S-K.

            We have reviewed the Company's  charter  documents and the corporate
proceedings taken by the Company with respect to the establishment and amendment
of the Plan.  With  respect to the  foregoing  documents,  we have  assumed  the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals and the conformity to originals of all documents submitted to us as
certified or reproduced  copies.  We also have obtained from the officers of the
Company certificates as to all factual matters necessary for the purpose of this
opinion and,  insofar as this opinion is based on such matters of fact,  we have
relied on such certificates without independent investigation.

            Based on such review,  we are of the opinion  that,  if, as and when
the  shares  of the  Company's  common  stock  are  issued  and  sold  (and  the
consideration  therefor  received)  pursuant to the  provisions  of the Plan and
stock option  agreements duly authorized  under the Plan, and in accordance with
the Registration Statement, such shares will be duly authorized, legally issued,
fully paid and nonassessable

            We consent to the filing of this  opinion  letter as Exhibit  5.1 to
the Registration Statement.

            This opinion  letter is rendered as of the date first  written above
and we disclaim any obligation to advise you of facts, circumstances,  events or
developments  which  hereafter  may be  brought to our  attention  and which may
alter,  affect or modify the opinion expressed herein.  Our opinion is expressly
limited to the  matters  set forth  above and we render no  opinion,  whether by




June 24, 2003
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implication or otherwise,  as to any other matters relating to the Company,  the
Plan, or the shares of the Company's common stock issuable under such plan.

                                         Respectfully submitted,


                              /s/ SHEPPARD, MULLIN, RICHTER & Hampton LLP