private boolean isInnerElement(TreeItem sourceTreeItem, Object investigationItem) {
		boolean isInnerElement = false;
		
		assert sourceTreeItem != null;
		
		if (investigationItem == null) {
			return false;
		}
		
		if (sourceTreeItem == investigationItem) {
			return true;
		}
		
		for (TreeItem childItem : sourceTreeItem.getItems()) {
			isInnerElement |= isInnerElement(childItem, investigationItem);
		}
		
		return isInnerElement;
	}