In a DUI case, the lookback period (or "washout period") is the length of time that a court will look back into a person's driving record for purposes of sentencing. So, for example, if the state in question has a 5 year look back, then any DUI conviction older than 5 years will not be considered as a prior conviction when the court determies the sentence to be imposed. Therefore if you only has 1 prior conviction but it was 7 years old, then you will qualify as a first-time offender (although the older conviction still remains on your record).