**Exhibit 31.1**

 

**CERTIFICATIONOF PRINCIPAL EXECUTIVE OFFICER**

**Section 302Certification**

 

I, Roger Heinisch, certifythat:

 
|    | 1.     |   |  I have reviewed this quarterly report on  Form 10-Q of American Science and Engineering, Inc.;                                                                                                                                                                                                                                                                                                                                                                     |
|--------------|--------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|         | 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;                                                                                                                                                           |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | 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;                                                                                                                                                                              |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | 4.     |   | The  registrant’s other certifying officer 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 we have:                                                                                                                                                                                                                                   |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | a)     |   | designed  such disclosure controls and procedures, or caused such disclosure controls  and procedures to be designed under our supervision, to ensure that material  information relating to the registrant, including its consolidated  subsidiaries, is made known to us by others within those entities,  particularly during the period in which this report is being prepared;                                                                                      |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | b)     |   | evaluated  the effectiveness of the registrant’s disclosure controls and procedures and  presented in this report our conclusions about the effectiveness of the  disclosure controls and procedures, as of the end of the period covered by  this report based on such evaluation; and                                                                                                                                                                             |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | c)     |   | disclosed in  this report any change in the registrant’s internal control over financial  reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) that  occurred during the registrant’s most recent fiscal quarter (the registrant’s  fourth fiscal quarter in the case of an annual report) that has materially  affected, or is reasonably likely to materially affect, the registrant’s  internal control over financial reporting. |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | 5.     |   | The  registrant’s other certifying officer 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 functions):                                                                                                                                                       |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | a)     |   | all  significant deficiencies and material weaknesses in the design or operation  of internal control over financial reporting which are reasonably likely to  adversely affect the registrant’s ability to record, process, summarize and  report financial information; and                                                                                                                                                                                       |
|         |   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|    | b)     |   | any fraud,  whether or not material, that involves management or other employees who have  a significant role in the registrant’s internal control over financial  reporting.                                                                                                                                                                                                                                                                                       |

 
| Date: August  13, 2003                         |
|------------------------------------------------|
|                                           |
|   /s/ Roger P. Heinisch                   |   |
| Roger P.  Heinisch                             |
| Interim  President and Chief Executive Officer |

 

 

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