A divided Michigan Supreme Court ruled on Friday that the state’s attorney general may investigate Eli Lilly over its pricing practices for insulin.

In its 4-to-3 decision, the court rejected a lower court decision that prevented Michigan Attorney General Dana Nesel from proceeding with a probe that began four years ago. At the time, Nessel cited state consumer protection laws, alleging the drug maker had artificially increased the price of its insulin medication.

Lilly was accused of charging “grossly” excessive prices for three different insulin products — Lispro, Humalog and Basaglar — that forced some patients to ration or forego insulin, restrict their diets or buy less-effective alternatives. These practices led to “serious disability and even death in some patients,” the state wrote in court documents at the time.