<PAGE>
(LETTERHEAD OF CAHILL GORDON & REINDEL)
June 29, 2000
Dean Witter Reynolds Inc.
Two World Trade Center
New York, New York 10048
Re: Morgan Stanley Dean Witter Select Equity Trust
Select Global 30 Portfolio 2000-3
----------------------------------------------
Gentlemen:
We have acted as special counsel for you as Depositor of the
Morgan Stanley Dean Witter Select Equity Trust Select Global 30 Portfolio 2000-3
(the "Trust"), in connection with the issuance under the Trust Indenture and
Agreement, dated September 30, 1993, as amended, and the related Reference Trust
Agreement, dated June 29, 2000 (such Trust Indenture and Agreement and Reference
Trust Agreement collectively referred to as the "Indenture"), between you, as
Depositor, and The Bank of New York, as Trustee, of units of fractional
undivided interest in said Trust (the "Units") comprising the Units of Morgan
Stanley Dean Witter Select Equity Trust Select Global 30 Portfolio 2000-3. In
rendering our opinion expressed below, we have relied in part upon the opinions
and representations of your officers and upon opinions of counsel to Dean Witter
Reynolds Inc.
Based upon the foregoing, we advise you that, in our opinion,
when the indenture has been duly executed and delivered on behalf of the
Depositor and Trustee and when the Receipt for Units evidencing the Units has
been duly executed and delivered by the Trustee to the Depositor in accordance
with the Indenture, the Units will be legally issued, fully paid and
nonassessable by the Trust, and will constitute valid and binding obligations of
the Trust and the Depositor in accordance with their terms, except that
enforceability of certain provisions thereof may be limited by applicable
bankruptcy, insolvency, reorganization, moratorium or other
<PAGE>
-2-
similar laws affecting creditors generally and by general equitable principles.
We hereby consent to the filing of this opinion as an exhibit
to the Registration Statement (File No. 333-37834) relating to the Units
referred to above and to the use of our name and to the reference to our firm in
said Registration Statement and the related Prospectus. Our consent to such
reference does not constitute a consent under Section 7 of the Securities Act,
as in consenting to such reference we have not certified any part of the
Registration Statement and do not otherwise come within the categories of
persons whose consent is required under said Section 7 or under the rules and
regulations of the Commission thereunder.
Very truly yours,
CAHILL GORDON & REINDEL
