Combobox object as a command parameter of a button

<telerik:RadComboBox x:Name="arresteeListPicker" ItemsSource="{Binding Arrestees}"
                                           DisplayMemberPath="ArresteeFullName"
                                         Placeholder="Arrestees"
                                         IsEditable="False">
                        
                        <telerik:RadComboBox.ItemTemplate>
                            <DataTemplate x:DataType="model:Arrestee">
                                <Label Text="{Binding ArresteeFullName}"
                                      ></Label>
                            </DataTemplate>
                        </telerik:RadComboBox.ItemTemplate>
                    </telerik:RadComboBox>
                    <Button x:Name="selectArresteeBtn"
                            Text="Select"
                            Command="{Binding SelectArresteeCommand}" 
                            CommandParameter= ?????????
                            WidthRequest="70"
                            HorizontalOptions="Start"
                            Margin="0, 10, 0, 0"
                            />