An important consideration of any commercial and industrial property acquisition or divestiture—whether it is a single gasoline station or a suite of oil refineries—is the extant environmental conditions of the property(s) at the time of the transaction. Property sellers and prospective buyers each consider and negotiate how any existing or future liability associated with extant environmental conditions will be handled. In spite of this forethought and the agreed contract terms, future litigation over unanticipated environmental contamination remains a real possibility. Often precipitating future litigation are disagreements surrounding whether “newly realized” contamination is old (pre-sale) or new (post-sale). As a result, environmental forensic investigations are often faced with the issue of “age-dating” this newly discovered contamination in order to determine whether it was released pre- or post-sale. Age-dating contamination can be an inherently difficult task to perform and technically defend. Technical arguments between experts can be short-circuited if there was an irrefutable understanding of the nature of extant contamination that had existed at the time of the sale. Conventional environmental due diligence investigations (Phase I and II site assessments) fall short of providing this understanding. In this paper, we discuss Strategic environmental baselining (SEB), a cost-effective and pro-active form of environmental due diligence that incorporates a key component of environmental forensics, that is, advanced chemical fingerprinting using modified EPA Methods that are tailored for hydrocarbon fingerprinting. Sufficient sampling and advanced chemical fingerprinting performed at the time of a transaction (or, at least, properly archived samples analyzed in the future as needed) provides the evidence that eliminates the need to “age-date” contamination at some future date. Advanced chemical fingerprinting data also provides detailed characteristics of the extant contamination and thereby, helps distinguish “old” from “new” contamination, regardless of alteration of the chemicals of concern by weathering. Armed with this information both buyers and/or sellers can protect themselves in the event of any future claim(s).