**EXHIBIT 31**

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**WAMU ASSET ACCEPTANCE CORP.**

**OFFICER’S CERTIFICATE**

 

I, David Beck, certify that:

 

1.  I have reviewed this report on Form 10–K and all reports on Form 10–D required to be filed in respect of the period covered by this report on Form10–K of WaMu Mortgage Pass-Through Certificates Series 2007-OA3 Trust(the ‘‘Exchange Act periodic reports’’);

 

2.             Based on my knowledge, the Exchange Act periodic reports, taken as a whole, do not contain any untruestatement 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, all of the distribution, servicing and other information required to be provided underForm 10–D for the period covered by this report is included in the Exchange Act periodic reports;

 

4.             Based on my knowledge and the servicer compliance statements required in this report under Item 1123 ofRegulation AB, and except as disclosed in the Exchange Act periodic reports, the servicers have fulfilled their obligations under the servicing agreement; and

 

5.             All of the reports on assessment of compliance with servicing criteria for asset-backed securities and theirrelated attestation reports on assessment of compliance with servicing criteria for asset-backed securities required to be included in this report in accordance with Item 1122 of Regulation AB and Exchange Act Rules 13a–18 and 15d–18 have been included asan exhibit to this report, except as otherwise disclosed in this report.  Any material instances of noncompliance described in such reports have been disclosed in this report on Form 10–K. 

 

In giving the certification above, I have reasonably relied on information provided to me by the following unaffiliated parties: American Security InsuranceCompany, Standard Guaranty Insurance Company and TrackSure Insurance Agency, Inc.

 

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 /s/ DavidBeck                                                                                                                  March 24, 2008 |
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| Signature of Authorized Officer                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       | Date |
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David BeckPresident and Senior Officer in Charge ofSecuritization of theDepositor                                                                                     December 31                                                                                                                    |
| Name and Title                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        | Company Fiscal Year-End |