EX-99.I 3 dex99i.txt JOINT FILING AGREEMENT Exhibit I Joint Filing Agreement pursuant to Rule 13d-1(k)(1)(iii) under the Securities and Exchange Act of 1934, as amended. Each of the undersigned hereby agrees to be included in the filing of the Schedule 13D dated March 13, 2003 with respect to the issued and outstanding Common Stock of Lexicon Genetics Incorporated beneficially owned by each of the undersigned, respectively. Dated: March 13, 2003 ESTATE OF GORDON A. CAIN By: /S/ MARY H. CAIN ------------------------------------ Mary H. Cain Co-Executor By: /S/ JAMES D. WEAVER ------------------------------------ James D. Weaver Co-Executor /S/ MARY H. CAIN ---------------------------------------------- Mary H. Cain /S/ JAMES D. WEAVER ---------------------------------------------- James D. Weaver /S/ WILLIAM A. MCMINN ---------------------------------------------- William A. McMinn