To succeed in a federal or statement trademark infringement lawsuit, the Plaintiff has the burden of showing a likelihood of confusion between his trademark and the Defendant’s trademark.  The Plaintiff must have a protectable trademark with an established priority date that precedes the accused infringer.

To determine if a likelihood of confusion exists in the market, the courts turn to the factors listed in the landmark Dupont case. Every jurisdiction has case law for determining how many factors to analyze, but the first 5 factors are followed in all jurisdictions. The Dupont factors are:

1. The similarity or dissimilarity of the marks in their entireties as to appearance, sound, connotation, and commercial impression.
2. The similarity or dissimilarity and nature of the goods . . . described in an application or registration or in connection with which a prior mark is in use.
3. The similarity or dissimilarity of established, likely-to-continue trade channels.
4. The conditions under which and buyers to whom sales are made, i.e. "impulse" vs. careful, sophisticated purchasing.
5. The fame of the prior mark.
6. The number and nature of similar marks in use on similar goods.  
7. The nature and extent of any actual confusion.
8. The length of time during and the conditions under which there has been concurrent use without evidence of actual confusion.
9. The variety of goods on which a mark is or is not used.
10. The market interface between the applicant and the owner of a prior mark.
11. The extent to which applicant has a right to exclude others from use of its mark on its goods.
12. The extent of potential confusion.
13. Any other established fact probative of the effect of use.