Refusing a breath test in Oregon results in a longer suspension than failing a breath test for the first time, however not having a breath test result will probably make it tougher for the state to win at trial. If your father is diversion eligible and goes that route the state won't have to prove anything as the diversion agreement requires a plea of guilty or no contest.
On the implied consent law, which results in the DMV suspension, you are probably right. On the criminal charge, I'd say your father was right.
In my opinion, you are right.
To me, the question hinges upon whether he is licensed to drive. If he has a license, he has already consented to a breath test, and his refusal to participate in a breath test can be used as evidence against him. In most cases a jury will tend to assume that his refusal to provide a sample is a sign of guilt, and as a practical matter he should be able to provide a believable reason as to why he refused to participate in an opportunity to show that he was actually below the legal limit. Although other lawyers may correctly point out that the state has the burden of proof in a criminal case, the reality is that many juries expect DUII defendants to be able to explain or justify their innocence.
In my opinion it doesn't really help his case that he refused to provide a breath sample, it makes it worse. In my experience it is easier to defend someone who has refused field sobriety tests and then provided a breath test sample.
This post is offered as general information and is not intended as legal advice. This information does not in of itself create any attorney-client relationship.
To add to the wise answers already here: the answer depends in part on your father's record. If, for example, he has 2 prior DUII convictions (no matter when they happened in his life -- let's say one at 21 years old, and one at 45) then he's now looking at a LIFETIME LICENSE REVOCATION and needs to do everything he can to help his case, including invoking his rights to silence and counsel and talking with a good lawyer before he decides to blow or not. If he's a big guy and he's only had a drink or two, he should blow (that is a complicated pharmocological decision phrased in a very simple way)! In the real world, however, most folks who refuse the breath test aren't thinking like that (i.e., like a lawyer/scientist); rather, they just get a bad feeling from an arrogant cop, or are being mistreated, or have "heard somewhere" that they should always refuse. Your father was right to have a feeling that the police were not "there to help." And in any event, he's your dad, love him, give the poor guy some support and get him a good lawyer!