[Here are the jury instructions](https://regmedia.co.uk/2016/05/26/google_oracle_jury_instructions.pdf).

These describe how to evaluate witness testimony, burdens of proof, and the four-factor fair use test, among other things.

The jury had to answer yes or no (unanimously) to the following question:

> Has Google shown by a preponderance of the evidence that its use in Android of the declaring lines of code and their structure, sequence, and organization from Java 2 Standard Edition 1.4 and Java 2 Standard Edition Version 5.0 constitutes a "fair use" under the Copyright Act?

They [answered yes](https://regmedia.co.uk/2016/05/26/oracle_jury_verdict.jpg). They did not need to explain their reasoning, but the assumption is that they followed the jury instructions to arrive at this conclusion.

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<sup>To be clear, the issue wasn't *reimplementation* of 37 Java APIs, but a more limited taking, including "the declaring
code and the structure, sequence, and organization".</sup>