Tosefta к Дмай 3:4

[One who] purchases [produce] from a boat [docked] in Jaffa or from a boat [docked] in Caesarea [others have ציפורי = Tzippori or Sepphoris] is liable [in the laws of Demai]. Rabbi Yehudah says, [all produce purchased from] the archway of the Yishuv and the archway of Antipatris and the marketplace of Patros originally was [considered] Demai, because there was a presumption that it was grown in the King's Mountain [cf. Y. Dem. V.8.6]. [But] now, our rabbis have held that [with respect to] all Samaritan towns that are by the side of the "Road" [per Lieberman here, the road running from from Judea to the Galilee], their grains and their legumes are [considered] Demai because they are of Israel [presumably, since Samaritans continue to consider themselves bound by the Written Torah, they may tithe such items, see Dem. 3:4, Dem. 5:9], but the remainder of their produce [as to which tithing is required by the Oral Torah, which Samaritans reject] is certainly untithed. [Note: משתמשין ביהודה, i.e., "used in Judea," should be stricken per the GR"A.]

[If a man] was trustworthy but his wife was not trustworthy, we may purchase [produce] from him but we may not be guests at his house, and [that is so] even though the [Sages] said, behold, he is like one who dwells with a snake in a wicker basket (i.e., his wife will control what is served and he will not interfere). [If] his wife is trustworthy but he is not trustworthy, we may be guests and his house, but we may not purchase [produce] from them. [If] he is trustworthy and one of his sons is trustworthy, or one of his (male) servants is trustworthy [see Lieberman, ואחד מעבדיו נאמן], or one of his female servants is trustworthy, we purchase [produce] and we eat [their produce at their homes] on their word [that their produce is tithed] and we prepare food for them. [But] during Shevi'it (the seventh year of the agricultural cycle, when fields must lie fallow) as as to Taharot (foods requiring preparation in a state of ritual purity), we are not allowed to do that (i.e., trust them at their word). [Note: Unlike a chaver, one who is "only" trustworthy is only trusted in regards to tithing, but not as to whether produce was grown during Shevi'it, or in matters of Taharot, see, e.g., Dem. 2:2, Dem. 2:3, Dem. 3:4.]