Exhibit 31.1

Rule 13a-14(a)/15d-14(a) Certification

I, Matthew H. Knight, certify that:

|1. | I have reviewed this Form 10-K/A
    of Strategic Diagnostics Inc. (the registrant);                                                                                                                                                                                                                               
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|2. | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;           
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|3. | Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;                              
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|4. | The registrants other certifying
       officers and I are responsible for establishing and maintaining disclosure
       controls and procedures (as defined in Exchange Act Rules 13a-15(e) and
    15d-15(e)) for the registrant and have:                                                                       
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|   | a)                                                                                                                                                                                                                                                                                                                   
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|   | b)                                                                                                                                                                                                                                                                                                                   
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|   | c)                                                                                                                                                                                                                                                                                                                   
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|5. | The registrants
      other certifying officers and I have disclosed, based on our most recent
      evaluation of internal control over financial reporting, to the registrants
      auditors and the audit committee of the registrants board of directors
    (or persons performing the equivalent function):
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|   | a)                                                                                                                                                                                                                                                                                                                   
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|   | b)                                                                                                                                                                                                                                                                                                                   

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|-------------------- | --- | ------------------------------------------------------
|Date: March 15, 2006 | By: | /s/ MATTHEW H. KNIGHT                                 
|                     |     |                                                       
|                     |     | Matthew H. KnightPresident and Chief Executive Officer



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