2] In fact, the authentication of the speed measuring device involves a compound determination. Before the machine is deemed reliable, the witness testing the machines or monitoring the testing must first show his/her 861*861 qualifications to make and/or evaluate the tests. The witness must first qualify as an expert via knowledge, skill, experience, training, or education. ER 702. After the witness has qualified as an expert, he/she must show that the machines passed the requisite tests and checks. Only then can the speed measuring devices be deemed reliable. Again, the questions concerning the expert's qualifications are preliminary matters governed by ER 104.