If I used a copyrighted image in 4 item listings on a selling platform (all using the same image), would this constitute 1 infringement, 4 infringements, or a number of infringements equal to the number of items sold?
In criminal law we might talk in terms of a number of "counts" of an offence. E.g. "the defendant is charged with 4 counts of copyright infringement".
However you've asked about civil law copyright infringement, so that isn't relevant. If you are sued, the claimant is not seeking to convict you of X number of offences. Instead, they are probably seeking some combination of the following:
- A mandatory injunction to compel you to remove the copyrighted material.
- A prohibitory injunction to prevent you from using the material again.
- Damages to compensate them for your past use of the material.
So, it is not useful to think about how many "infringements" there were as such. What matters is the extent and circumstances of the infringement insofar as it is relevant for determining how much damages should be awarded. For example, in england-and-wales, section 97(2) of the Copyright, Designs and Patents Act 1988 provides:
The court may in an action for infringement of copyright having regard to all the circumstances, and in particular to—
(a) the flagrancy of the infringement, and
(b) any benefit accruing to the defendant by reason of the infringement,
award such additional damages as the justice of the case may require.
In the european-union, article 13(1) of the Enforcement Directive 2004/48/EC provides:
Member States shall ensure that the competent judicial authorities, on application of the injured party, order the infringer who knowingly, or with reasonable grounds to know, engaged in an infringing activity, to pay the rightholder damages appropriate to the actual prejudice suffered by him as a result of the infringement.
When the judicial authorities set the damages:
(a) they shall take into account all appropriate aspects, such as the negative economic consequences, including lost profits, which the injured party has suffered, any unfair profits made by the infringer and, in appropriate cases, elements other than economic factors, such as the moral prejudice caused to the rightholder by the infringement; or
(b) as an alternative to (a), they may, in appropriate cases, set the damages as a lump sum on the basis of elements such as at least the amount of royalties or fees which would have been due if the infringer had requested authorisation to use the intellectual property right in question.