When to conduct an IT audit

Is it more advantageous to conduct a pre-implementation IT audit during development or after inplementation? There are times that you will want to audit a new application while it is in development to ensure that the new application, or system, will be delivered on time and within budget. However, there are also advantages in auditing an application or new system, after it has been implemented or installed and operational for at least 3 to 6 months. You will be in a position to attest to the operational effectiveness and quality of the product that has been delivered. If it is decided that both audits are valuable and the application or system is audited at both times by a team of auditors performing both audits, then an issue surfaces. How do you ensure that the auditors have adequate segregation of duties and are not auditing their previous audit results and recommendations? One solution, if both audits are to take place, is to have the two audits performed by two different audit teams to mitigate the exposure of conflict of interest and segregation of duites.