Exhibit 1.1 VAN KAMPEN UNIT TRUSTS, SERIES 820 TRUST AGREEMENT Dated: December 9, 2008 This Trust Agreement among Van Kampen Funds Inc., as Depositor, The Bank of New York Mellon, as Trustee, Van Kampen Asset Management, as Supervisor, sets forth...Trust Agreement • December 9th, 2008 • Van Kampen Unit Trusts Series 820
