When you have a pie chart, its slices are technically regions with shapes. When you click on a slice, a different slice is often picked, you can also pick slices outside of the chart, because the slices are picked "on bounds" - this is caused by RT-17024 (region picking on bounds by default). However, when you set slice's pickOnBounds to false manually, it doesn't help, because the hit test is wrong. I experimented and found out that the area outside of the slice is picked because of the code branch in Region's picking that says:

                            // pt within fill and not within area with a rounded corner either because
                            // there are no rounded corners or the pt doesn't fall inside one

Here is a code to reproduce the problem:

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.chart.PieChart;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class PieChartExample extends Application
{
private void init(Stage primaryStage)
{
Group root = new Group();
primaryStage.setScene(new Scene(root));
PieChart p = createChart();
root.getChildren().add(p);
}

protected PieChart createChart()
{
final PieChart pc = new PieChart(FXCollections.observableArrayList(
new PieChart.Data("Apples", 40),
new PieChart.Data("Strawberries", 11),
new PieChart.Data("Grapes", 30),
new PieChart.Data("Oranges", 10)
));
// setup chart
pc.setId("BasicPie");
pc.setTitle("Fruits");

for (final PieChart.Data data : pc.getData())
{
data.getNode().setPickOnBounds(false);
data.getNode().setUserData(data.getName());
data.getNode().addEventHandler(MouseEvent.MOUSE_PRESSED,
new EventHandler<MouseEvent>()
{
@Override
public void handle(MouseEvent e)
{
if(e.getSource() instanceof Node)
{
Node node = (Node)e.getSource();
System.out.println("Slice: " + node.getUserData()+ " hashCode: " + node.hashCode());
}
}
});
}
return pc;
}

@Override
public void start(Stage primaryStage) throws Exception
{
init(primaryStage);
primaryStage.show();
}

public static void main(String[] args)
{
launch(args);
}
}