The technology giant's design was able to provide important evidence in the trial of Hussein K, thanks to some of the features that are pre-installed on the iPhone 6S and newer models.
The refugee was accused of the rape and murder of Maria Ladenburger, who was killed in October 2016.
Hussein admitted his guilt but disputed some details of the police's accusations.
However, Apple's Health App has been used to inform the investigation, including nutrition and sleep patterns.
Peter Egetemaier, the chief of police, told the court, according to German paper Die Welt: "For the first time, we correlated health and geo-data."
Hussein's age - which is unknown - is complicating the trial, because it will be used to determine his sentence.
Meanwhile, Apple recently announced plans to make parental control tools more robust after calls to take action against smartphone addiction in children.
A pair of investors - who collectively control $2 billion in Apple stock - blasted the firm for not doing anything to prevent the growing concerns around the negative effects of smartphones.
In response, Apple said: "Apple has always looked out for kids, and we work hard to create powerful products that inspire, entertain, and educate children while also helping parents protect them online.
"We have new features and enhancements planned for the future, to add functionality and make these tools even more robust.
"We think deeply about how our products are used and the impact they have on users and the people around them.
"We take this responsibility very seriously and we are committed to meeting and exceeding our customers' expectations, especially when it comes to protecting kids."