Can a refusal be challenged if the officer didn't read the warning correctly?

Yes. The implied consent advisory under § 31-27-2.1 must be substantively complete and accurate. If the officer failed to inform the driver that refusal would result in license suspension, omitted the duration of suspension, or misstated the penalties, the refusal charge can often be challenged. Before sustaining a refusal, the judge must find that the driver was informed of the penalties in the implied consent notice (§ 31-27-2.1(d)(4)).