Police should use Saliva testing for at least the following reasons. And when other options are better suited than saliva testing.
Non-Invasive:
Saliva drug testing is non-invasive and requires minimal effort from the police officer. In contrast, a urine test may require the officer to provide a urine sample, which can be inconvenient or uncomfortable. It can take several hours for a person to be willing or able to give a urine sample. A saliva sample can be taken in minutes. A blood test means you have to take the person in and get the blood drawn then send it in to get tested. So saliva drug testing is much simpler and less invasive than either urine or blood drug testing.
Quick Results:
Collecting a saliva sample is quick and easy, taking only a few minutes to complete. In contrast, collecting a urine sample can take longer as the individual may need to wait until they have enough urine in their bladder. Additionally, collecting a urine sample can be more invasive and require more privacy, which can take additional time. Saliva drug testing is often more convenient for both the person being tested and the tester. Saliva drug tests can be administered virtually anywhere and require no special equipment or facilities. In contrast, urine drug tests require access to a bathroom and may need to be conducted in a private setting. Saliva drug tests are highly accurate and have a low chance of producing false positives. In contrast, urine drug tests can be prone to producing false positives due to the many ways one could fake the test.
Detection Window:
Saliva drug tests are good at detecting recent drug use, typically within the past 24-48 hours. This can be important for police officers who may be requiring those they are testing to be drug-free recently and for whom recent drug use may be more relevant than use from several days prior. A saliva drug test is better than a urine test when considering the detection window comparison because it has a shorter window of detection than urine. Saliva drug tests can typically detect drug use within the past 24-48 hours, whereas urine tests can detect drug use up to several days or even weeks after use. This is because drugs and their metabolites are excreted from the body in urine at a slower rate than they are in saliva. For police officers, a shorter detection window is often preferred because it can provide more recent and accurate information about whether someone has used drugs recently. To understand better if they are currently under the influence instead of days prior.
Saliva testing is not the end all.
If you are testing for a pure alcohol DUI then a breathalyzer is quick and easy. in many cases holds up in court better because laws are out there saying alcohol content up to a certain level is fine. Saliva testing will show you it is there even in small amounts. And it would even turn up if you used an alcohol based mouthwash and swallowed none of it. So even though we think Saliva testing is very useful for police officers there are other tools that are still needed in certain cases.
Difficult to Cheat:
Saliva drug testing is non-invasive and requires minimal effort from the person being tested, which reduces the chances of tampering or substitution. Simple Saliva drug tests can be administered under direct observation, which reduces the possibility of substitution or adulteration of the sample. Saliva drug tests can be performed immediately, which means that the person being tested cannot adulterate or substitute their sample beforehand. These features make saliva drug testing a more reliable and secure method of drug testing.
Bakersfield police are proof it works. See there story here.
There are more reasons like you do not need very much training and those who are taking it are more likely to give you less of a hassle.