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**EXHIBIT      31.1**

**CERTIFICATIONS**

| 1. | I                have reviewed this quarterly report on Form 10-QSB for the quarter                ended June 30, 2005 of Atlas America Public #12-2003 Limited                Partnership. |
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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 officer(s) 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)) and internal                control over Financial Reporting (as defined in Exchange Act Rules                13a-15(f) and 15d-15(f)) for the registrant and                have: |
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|  | 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; |
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|   | b) | Designed                  such internal control over financial reporting, or caused such                  internal                  control over financial reporting to be designed under our supervision,                  to                  provide reasonable assurance regarding the reliability of financial                  reporting and the preparation of financial statements for external                  purposes in accordance with generally accepted accounting                  principles; |
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|  | c) | 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 |
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|  | d) | Disclosed                  in this report any change in the registrant’s internal control over                  financial reporting 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; and |
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| 5. | The                registrant’s other certifying officer(s) 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): |
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|  | 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 |
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|  | 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. |
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| By:          | /s/                  Freddie M. Kotek                                    |
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| Name:        | Freddie                  M. Kotek                                        |
| Title:  | Chief                  Executive Officer of the Managing General Partner |
| Date:        | August                  15, 2005                                         |

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