public String getResponse() {
        System.debug('I am in!');

        if(validate()) {
            Visitor newVisitor = new Visitor();
            newVisitor.Name = 'John Smith';
            newVisitor.Identifier = 'john@somewhere.com';
            insert newVisitor;
            return '{"success":"true"}';
        }

        return '{"success":"false"}';
    }

Visitor__c newVisitor = new Visitor__c ();
newVisitor.Name = 'John Smith';
newVisitor.Identifier__c = 'john@somewhere.com';
insert newVisitor;

try
{
    insert newVisitor;
}
catch( DmlException ex )
{
    // fail gracefully
}

try
{
        Database.SaveResult[] MySaveResult = Database.Insert(newVisitors, false);
}
catch( DmlException ex )
{
        // fail gracefully
}